The accuracy of milk progesterone assay for the early diagnosis of pregnancy in dairy cows and buffalo-cows was assessed using a radio immunoassay technique for determination of progesterone concentration in the whole milk of those animals 24 days after service. This was based upon the subsequent confirmation of occurrence of pregnancy by rectal examination 2 months after breeding. In case of non-pregnancy, the hormone assay was 100% accurate. The efficiency of the test in identifying pregnant cons and buffalo-cows was 85.7% and 87.5% with progesterone concentrations ranged from > 2 to 13 ng/ml and >1 to 9 ng/ml of milk of both animals, respectively. Different consider ations in the interpretation of the test results were also discussed.