Surveys undertaken on diseases caused by Vibrio spp. in Penaeus monodon from culture ponds of coastal Andhra Pradesh recorded the occurrence of five types of diseases : tailnecrosis,shelldisease,reddisease,looseshellsyndrome(LSS), and white gut disease(WGD). Amongthese,LSS,WGD,and red disease caused mass mortalities in shrimp cultureponds. Six species of Vibrio V.harveyi,V.parahaemolyticus,V.alginolyticus,V.anguillarum,V.vulnificus,and V.splendidus are associated with the diseased shrimp. The number of Vibrio spp. associated with each disease ranged from two to five. Additionally,shrimp with red disease had concurrent infections with white spot syndrome virus.Vibrio harveyi in the case of LSS and WGD, V. parahaemolyticus for reddisease, and V.algino-lyticus for shell disease are the major etiologcalagents. Differences occur in the degree of virulence of different species of Vibrio and also different isolates of the same species. Vibrioharveyi isolated from LSS shrimp is the most virulent.Ingeneral, allthe Vibrio isolates from LSS shrimp tend to be more virulent as compared to their counter parts fromo the diseased shrimp.It is apparent that the degree of virulence of various Vibrio isolates depends on its source and the pond environmental conditions. Most of the Vibrio isolates showed susceptibility to oxy-tetracycline, norfloxacin, and ciprofloxacin. The luminous V.harveyi exhibited resistance to many antibiotics and susceptibility to only three drugs. Considering the emergence of antimicrobial resistant strains of Vibrio, the need for using probiotics in place of antibiotics for disease control is stressed.