Abstract Peripheral lymphocytes were obtained from five normal healthy adults. T and B lymphocytes were separated by rosette formation. LDH (L-lactate:NAD + oxidoreductase, EC 188.8.131.52) isozymes were studied on both populations after agar gel electrophoresis. The mean B lymphocyte pattern was: LDH-1, 7.2%; LDH-2, 25.0%; LDH-3, 39.2%; LDH-4, 21.9%; LDH-5, 6.6%. The mean T lymphocyte pattern was: LDH-1, 25.8%; LDH-2, 35.1%; LDH-3, 28.3%; LDH-4, 9.4%, LDH-5,1.3%. This makes the T lymphocytes look more aerobic than the B lymphocytes. Daudicells had the following pattern: LDH-1, 8.4%; LDH-2, 19.1%, LDH-3, 26.6%, LDH-4, 24.9%; LDH-5, 20.9%.