The psychometric characteristics of two indexes used to evaluate the subjective morbidity of chemotherapy regimens were analyzed. Both indexes assessed the duration of discomfort as perceived by the patient throughout therapy. The first index asked patients to state the number of days spent with 'discomfort', and the second index asked them which days they would like to eliminate altogether because of the unbearable symptoms experienced on those days. While the first index gives some idea of the duration of suffering, without defining it, the second highlights a specific time when the quality of her life was unacceptable to the patient. We studied these indexes in the form of a questionnaire completed by 168 women who had entered a cancer clinical trial. This trial evaluated the efficacy of primary chemotherapy in rendering conservative surgery feasible in women with operable breast cancer, but whose tumor size was greater than 3 cm. Four different treatment regimens were used: CMF, FAC, FEC, FNC (C = cyclophosphamide, M = methotrexate, F = fluorouracil, A = adriamycin, E = epirubicin, N = mitoxantrone). Seventy-nine patients were interviewed during chemotherapy and 89 during follow-up visits. Initial assessment of the reliability, discriminant and concurrent validity of the two indexes produced satisfactory results. Finally, we analyzed the responses given by 168 patients for a total of 600 treatment cycles. The average value of 'discomfort' was 3 days, whereas the average value of days 'to be eliminated' was 1. The range of subjective morbidity (for every cycle of treatment: 'discomfort = 0-30 days; 'to be eliminated' = 0-20 days) was very broad.(ABSTRACT TRUNCATED AT 250 WORDS)