The cell-free extracts of 60 strains which were identified phenotypically as being those of Lactobacillus brevis, including 48 isolates from the environment and 12 reference strains, were applied to polyacrylamide gel electrophoresis for extracting their NAD-dependent D- and L-lactate dehydrogenases (LDH). These strains were divided into 5 groups, i.e., Groups A, B, C, D, and E, on the basis of the electrophoretic mobilities of their D-LDH. The strains showed variations in their carbohydrate fermentation patterns. No relationship between the profile of D-LDH and the carbohydrate fermentation pattern was recognized. However, there appeared to be a relationship between the D-LDH profile and the beer-spoilage ability, because 40 out of 44 beer-spoilage strains identified as L. brevis were classified to Group E. We purified D-LDHs from the so-called complete beer-spoilage strain SEC 8002 of LDH Group E and from the non beer-spoilage strains JCM 1059(T) of LDN Group A and AHU 1508 of LDH Group C. Although the purified D-LDHs had the same molecular weight (84 kDa), each possessed a different optimum pH, optimum temperature, and isoelectric point. The aforementioned parameter values for the enzyme from the so-called complete beer-spoilage strain SEC 8002 of LDR Group E were 10.0, 50 degrees C, and 4.1, respectively; this strain was discriminated from the D-LDHs of the other tao non beer-spoilage strains especially by its optimum temperature (50 degrees C).