Serum immunoglobulin levels were periodically determined in 70 CLL patients and the changes were correlated with several clinical and laboratory parameters. It was found that the lgG and IgA levels decreased significantly as the disease progressed. A low lgG concentration was found at the time of diagnosis in 18.7% and after six years in about 50% of the patients. The IgM concentration, although initially low, increased during the follow-up in 43% of the patients and in four of them a monoclonal fraction appeared in the serum. The changes in the immunoglobulins did not correlate with age, sex or initial leukocyte count. Stage 0 patients as well as untreated patients also had a decrease in their immunoglobulin levels but advanced disease stage and especially continuous chemotherapy seemed to augment the drop in the immunoglobulin levels. Neither the initial immunoglobulin levels nor the subsequent changes, absolute or 75° position. Maximal static expiratory pressure decreased after dialysis although the statistical significance of this result was only borderline (p = 0.07). Hand-grip pressures also decreased (p = 0.005) following dialysis. The results of this study indicate that chronic renal failure patients undergoing maintenance hemodialysis have predialysis abdominal and thoracic muscle weakness with further abdominal weakening postdialysis. The results also indicate that other muscle groups (such as those of the hand and arm) weaken during hemodialysis.