Histological studies on the gonads of Epinephelus diacanthus collected off Quilon and Ratnagiri west coast of India, revealed protogynous hermaphroditism and the presence of seven transitional stages. The transitional gonads were found to be intermixed with the spermatogonia and spermatocytes within the ovarian lamellae. The smallest size of the transitional E. diacanthus was 27.5 cm total length and the largest was 31.4 cm TL. The weight range was 362-430 g. Histologically recognized transitional E. diacanthus showed size related variations from the two geographically different regions.