The aim of the study was to investigate the importance of ADA serum and its isoenzyme activity in diagnosing white muscle disease in lambs. The animal material used in the study was forty seven Akkaraman lambs - twenty seven of which had clinical signs of white muscle disease (white muscle disease group) and twenty healthy lambs (control group). Blood samples were taken and Se levels, CK, LDH, AST, ADA and ADA izoenzyme activity were determined. Following this, the animals in the white muscle disease group received I mg sodium selenit + 60 mg vitamin E intramuscularly as a single dose. Fourteen days following sodyum selenit + vitamin E application blood samples were again taken and the same analysis repeated. Apart from ADA2 activity, other enzyme activities were significantly high (p < 0.001), and serum Se concentrations were significantly low (p < 0.001) in animals of the white muscle disease group compared to the control group. When the parameters obtained from the white muscle disease group were compared before and after treatment it was indicated that all enzyme parameters decreased significantly (p < 0.001) after treatment. On the other hand, serum Se concentration increased (p < 0.01) after treatment in the diseased group. The results confirm that determining ADA serum and its isoenzymes, together with CK, LDH and AST values seems to be useful in diagnosing white muscle disease.