Chemotherapy side effects, patient distress, and patient-practitioner communication were evaluated in an inception sample of 238 patients with breast cancer or malignant lymphoma. Participants were interviewed at five points during their first six cycles of therapy, and a subsample kept brief daily symptom diaries. Nausea, hair loss, and tiredness were each experienced by more than 80% of patients. By cycle 6, 46% of patients had thoughts about quitting therapy, but only a few had told medical staff. Patients' ratings of the objective difficulty of treatment increased over time, varied by treatment regimen, and were predicted by the experience of side effects, with the number of different side effects serving as the best predictor. In contrast, emotional distress was less sensitive to the directly assessable characteristics of treatment. Communication between patient and practitioner was found to be inadequate in a number of respects (i.e., patients did not fully anticipate the toxicities of treatment and did not report their concerns to medical staff). Communication may be impeded by inaccuracies in a patient's recall of treatment difficulties and by a patient's inability or unwillingness to attend to all presented information. More frequent opportunities for patient-practitioner discussion are necessary.