The present investigation was conducted to study the accuracy of serum progesterone assay in diagnosing early pregnancy. Twenty healthy graded Murrah buffalo cows aged 4-8years were selected and inseminated using frozen semen upon observation of heat signs. They were subjected to early pregnancy diagnosis on 21d post insemination using ELISA based serum progesterone assay. Out of 20 buffaloes tested for serum progesterone concentration, 9 (45%) were diagnosed as pregnant and 11 (55%) as non pregnant. The animals were diagnosed pregnant and non pregnant if the progesterone values were 2.5 or >2.5 ng/ml and <2.5ng/ml, respectively and the progesterone concentrations in the buffaloes found pregnant ranged between 2.54 to 7.63 ng/ml and the same in non pregnant buffaloes ranged between 0.63 to 1.9 ng/ml. Serum progesterone concentration of pregnant and non pregnant animals differs significantly (P<0.05). From this study it was concluded that serum progesterone assay was 80 per cent accurate in diagnosing early pregnancy and 90 per cent for non pregnancy with an overall diagnostic accuracy of 85.0 per cent.