For the purpose of reevaluating diagnostic usefulness of total and prostatic serum acid phosphatase levels in patients with prostatic carcinoma, change of these levels was studied in 110 randomly selected patients, of which 35 were untreated prostatic carcinoma cases. Following hyperglycemic treatment, both levels in untreated prostatic carcinoma patients decreased significantly to their pretreatment levels and this test was a useful tool for diagnosis in the patients with prostatic carcinoma.