When Nell Dunn's father was dying at home in great pain of a severe cancer, she found she was unable either to care for him physically or talk to him about what was going on. You would think that the author of Up the Junction and Poor Cow wouldn't have a problem with empathy and kindness, but Dunn feels that she has always been hopeless at it.

"My father didn't have a good death," she says. "I didn't know how to help him. I have never known how to support someone through a crisis and I wanted to be better at it, so I wrote the play Cancer Tales in order to learn how other people managed. I worked from the outset with director Trevor Walker, trying to create a dramatic form which authentically represented the lives of the people I had talked to."

Cancer Tales is a series of monologues/dialogues - verbatim theatre, the voices of seven women and one man whose lives have been affected by cancer. Dunn calls them love stories, as they demonstrate what happens to relationships in the face of disaster. But with any life-threatening illness, not just cancer, your private life becomes public and you must also relate to doctors, nurses and many other members of the medical profession, some of whom may not be much good at relating either.

Dunn is fiercely opposed to "doctor bashing". "We're expecting doctors to have a depth of kindness that I certainly haven't got," she says. "I'm impatient, irritable, forgetful, but they must be tremendously intelligent, generous and never forget anything. Some are not going to manage it. They are dealing, every day, with people who are depressed, ill, miserable, angry and frightened, and who need different things: "Tell me everything"; "Don't tell me my son's going to die"; "Spend more time explaining"; "I don't want to talk to the doctor". Doctors have to feel their way. They make blunders because they're in the front line. We're hoping that doctors and nurses can be straightforward and kind all the time, but they can't. Why? Because they are often exhausted, working in a badly run system, overstretched, and to be generous every day is beyond human possibility."

But is kindness something that can be taught? Actors are now being used in medical schools to role-play patients and then give medical students feedback. Cancer Tales has been performed for doctors, medical students and Macmillan nurses, and been very well received. It perhaps helps by illuminating the little things that make such a huge difference. "I asked the anaesthetist: 'Please will you whisper in my ear now and then that I'm doing very well'," says Clare, one of the characters in the play, "and she said, 'I will, even if they laugh at me.' Also, when I was in the pre-op room, and they were putting needles in my veins, Mr Lawrence came out of the operating theatre wearing his funny little hat and said, 'I want you to see. Look, I'm here.' It says everything, doesn't it? He had a brusque manner ... very gung-ho and matter of fact, yet he had that sensibility."

Later, in a crowded radiotherapy waiting room, a young doctor must tell Clare about using a dilator to make her vagina stay open. She has never met this man before. "I'm feeling absolutely shattered," she says, "I'm falling apart and trying not to show it, but I'm in a small space and all these people could hear everything. The women looked interested, the men hid their faces in their hands. I know the young doctor is doing his best in an impossibly undignified situation."

"It's specially tough for the parents of grown-up children," says Mary, whose daughter Rebecca is dying. "You have a role but you can't really make any important decisions. It's very confusing how to be and where to be ... I had to step back and not take control of her life. She wanted to be treated as a living person, not as a dying person."

Dunn was in the position of a writer and outsider, but the people she was observing, stuck in the reality of serious illness, had to work it out for themselves, yet managed, somehow, in the most harrowing of situations, to be loving and generous. Joan had great difficulty looking after her adult son, who she could not believe was really ill. He kept hitting her - "Not hard, just a sly punch" - and shouting at her. "I was frightened to be alone with him, but he says, 'Mum, you've got to give me a bath.' I felt awful about that ... I'd never seen him with no clothes on since he was little ... anyway I help him, and I wash his back and he has a real nice bath ... next day he wanted to go back to hospital and he never came out."

When life really does become too short, you can't mess about any more, and every conversation takes on a heightened sensitivity. "But our job is not to be overwhelmed by someone's misery," says Dunn. "We can acknowledge it, but still come in with good news about the outside world. If I went to the pictures last night and had a good time, I'm allowed to say so. Before I wrote this, I didn't know how to ask for support or how to give it," she says. "I'm managing better now, because I've learned how other people do it. Perhaps there isn't any extraordinary training - we just need to be straighforward and be ourselves. It's less exhausting."

Cancer help

· Maggie Cancer Care Centres (0131 537 3131). Support centres offering information, psychology sessions, relaxation (breathing techniques, visualisation). Two operational centres in Edinburgh and Glasgow. Opening in Dundee September 2003 and in London 2004.

· CancerBACUP (www.cancerbacup.org.uk; 0808 800 1234). Information for patients, family and friends. Drop-in centres in hospitals in London, Coventry and Manchester.

· Hospice and Palliative Care (www.hospiceinformation.info; 0870 903 3903)

· St Christopher's Hospice (51 Lawrie Park Road, London SE26; 020-8768 4500). Care provided in a hospice, hospital, day centre or at home.

· Cruse Bereavement Care (www.crusebereavementcare.org.uk; 0870 1671677). Support, information and advice and possible one-to-one support. Also offers training.

· Macmillan Nurses (www.macmillan.org.uk; 0808 8082020). Expert care and practical and emotional support. Raises funds for specialist nurses and doctors, builds cancer centres, gives financial help, provides range of information.

· Samaritans (08457 909090).

· Cancer Tales is at the Greenwood Theatre, Guy's Campus, Weston Street, London SE1, from Friday May 16, to raise money for a new Maggie Centre. Box office: 020-7848 2929. Cancer Tales, by Nell Dunn, is published by Amber Lane Press, price £7.99.