Three hundred and sixty-nine patients in an MRC study of combination chemotherapy and radiotherapy for small-cell lung cancer of limited extent were asked to complete a Daily Diary Card which enabled an assessment of their quality of life to be made during and after treatment. The information derived from the card suggests that although cytotoxic chemotherapy has an adverse effect upon quality of life, this impairment only affects the first 2 or 3 days following each course of treatment, although there is also a small deterioration which may be associated with the ‘nadir’ effect of the blood counts about 10 days after each course. These results should assist physicians in counselling patients about the likely effects of treatment. Just over half of the patients (196) were subsequently randomised to either a further six courses of maintenance chemotherapy or no further chemotherapy, and it is also shown that the patients allocated to no maintenance chemotherapy experienced a gradually deteriorating quality of life, as opposed to the brief but more severe adverse effects which occurred following each course in the maintenance chemotherapy group; this supports the hypothesis of a palliative effect in this latter group. The findings demonstrate that the Daily Diary Card is a sensitive instrument capable of yielding useful information.