A quantitative biochemical and histochemical study of the alcohol dehydrogenase activity of pea cotyledons indicated that the enzyme activity decreased about 40 % during the first seven days of germination. The enzyme is formed during seed development and is reactivated by hydration only during germination. During homogenization of cotyledons of peas germinated for several days, substances are liberated which inactivate the enzyme. These substances – very probably long-chain fatty acids – are absent in the intact cotyledons and are also absent in the cotyledons and homogenates of seeds germinated for one day. To ascertain the alcohol dehydrogenase activity of cotyledons of peas germinated for several days, it is necessary to add bovine serum albumin to the extraction medium or to avoid homogenization of the tissue by using a histochemical method.