Questionnaires on the quality of life and tolerance of different parts of maintenance treatment were sent to a total of 83 patients with multiple myeloma. All patients were for more than one year on maintenance treatment which involved either interferon alpha monotherapy (I), 3 million u. three times per week till signs of relapse developed or sequence administration of interferon alpha and dexamethazone 40 mg on day 1 to 4, 10 to 13 and 20 to 23 and then after a four-week interval again interferon alpha, again till progression of the disease occurred. The patients evaluated the presence or absence of different undesirable effects of treatment during the first two weeks of treatment and throughout the year and listed their intensity into four categories defined in the questionnaire. The quality of life was evaluated by means of a basic module of the questionnaire of the European Organization for Research and Treatment of Cancer Core Quality of Life Questionnaire version 3.0 (EORTC QLQ-C30). The results of the questionnaire are to a certain extent surprising as from the patients' answers ensues that this maintenance treatment is associated with more numerous undesirable effects than the physicians realized when in contact with the patient. In this summary we can list only the most frequent effects (deterioration of eyesight, impaired sleep, depressions, irritability and unrest, chill, pain in muscles and joints, general weakness and dyspnoea). From the questionnaires on the quality of life ensues a markedly poorer quality of life of these patients as compared with the healthy population. There are however no basic differences between individual groups. The questionnaires were handed only to patients who had maintenance treatment for more than one year and thus patients were eliminated where maintenance treatment was discontinued because of undesirable effects. To give a general idea of the tolerance of the above maintenance treatment the authors mention that to the date of Aug. 31, 2001 113 patients were randomized into one of the branches of maintenance treatment. Maintenance treatment had to be discontinued in 6% patients (in two instances on account of severe hypothyroidism, in one case on account of hallucinations, in three instances on account of severe mental depression caused by this treatment). Reduction of interferon doses in 20% patients usually because of cytopenia but also on account of psychic problem. To the question what length of prolongation of life compensates the undesirable effects of maintenance treatment the following replies were obtained from patients receiving ID, possibly I: 3 months--47.6 and 38.3%, 6 months--4.3 and 10.6%, 9 months--0 and 4.3%, 12 months--47.6 and 46.8% of the addressed patients. In reply to the question whether the patients would prefer, assuming equal effectiveness, a maintenance monotherapy with interferon alpha or dexamethazone more patients preferred interferon to dexamethasone. For practice ensues from this article informing on undesirable effects of maintenance treatment and the effect of maintenance treatment on the quality of life: 1. the necessity of thorough knowledge of physicians of all possible undesirable effects as only a doctor knowing possible undesirable effects of treatment can recognize them, 2. regular monitoring not only of the activity of the basic disease, but also undesirable effects of maintenance treatment and the influence of treatment on the patients' quality of life, 3. the necessity to assess the quality of life in clinical trials as an important parameter for deciding on the way of treatment.