The outcomes of the work under FAO project TCP/VIE/3304 on the diagnosis of bacteria isolated from shrimp affected by early mortality syndrome/acute hepatopancreatic necrosis syndrome (EMS/AHPNS) in Viet Nam are presented. Field sampling was conducted in Soc Trang, Bac Lieu and Ca Mau provinces. At each sampling location, the targeted samples included three infected and three non-infected ponds. Disease signs at the pond level included pale hepatopancreas (HP), significant atrophy of the HP, guts with discontinuous contents or no content; onset of clinical signs and mortality starting as early as 10 days post stocking. At the end of the sampling campaign, shrimp from a total of 36 infected and 24 non-infected ponds had been collected. A total of 175 Vibrio isolates were isolated from the HP of shrimp specimens. A majority of isolates were identified as Vibrio parahaemolyticus by using API 20E kit and 16S rRNA sequencing. Thirty isolates of V. parahaemolyticus from each province were subjected to rep PCR analysis and detection of Tlh, Tdh and Trh genes. Rep PCR resulted in at least four different DNA profiles for the tested isolates. The Tlh gene was detected from all tested isolates, but neither the Tdh nor the Trh gene.