Heavy mortalities due to luminescent vibriosis have been observed among pond-cultured Penaeus monodon shrimp in the Philippines. The species composition of luminescent Vibrio associated with mortalities was determined. A total of 189 luminescent bacteria isolated from the hepatopancreas of affected shrimps, rearing water and seawater from different shrimp farms in 11 provinces of the Philippines were examined for their morphological, physiological and biochemical characteristics. Results revealed a varied composition of Vibrio species. The most dominant luminescent Vibrio species was V. harveyi (65.5%) followed by V. logei (7%), Photobacterium sp. (6%) and V. orientalis (1%). Some isolates, based on their characteristics, were identified as V. campbellii (16%), V. mediterranei (3%), V. fluvialis (0.5%), V. cholerae (0.5%) and V. splendidus II (0.5%), which are known as non-luminescent Vibrios. V. harveyi is thought to be the major etiological agent associated with the luminescent vibriosis in pond-cultured P. monodon and its pathogenicity was confirmed through intramuscular injection to shrimp. Experimental infection showed that V. campbellii was also pathogenic to P. monodon.