This study aimed to investigate the quality of effluent water of a large shrimp farming complex in Chabahar region in Sistan and Baluchestan province (Iran). Fifteen sampling stations were designated in three distinct areas of these farms i.e. the water supply canal, the drainage canal and the receiving area of the farm effluents in Gwatar Gulf. Water samples were taken from June to December 2004 for measurement and monitoring of nitrate, nitrite and ammonia compounds. The results revealed that the shrimp farms effluents have a profound effect on the water quality and aquatic environment of the drainage canal and the Gwatar Gulf. The average concentration of nitrate, nitrite and ammonia remained considerably higher in the drainage canal and Gwatar Gulf compared to the supply canal throughout the study. The amount of these compounds increased considerably in the drainage canal during the final stages of culture period and in Gwatar Gulf at post monsoon. The results of one way analysis of variance (at P<0.01 level) showed that all physical and chemical factors except water temperature were significantly different between stations. Considering that more than 25% of the shrimp farms of this complex were active during this study the measured values of nitrate, nitrite and ammonia compounds in the effluents were at the optimum range recommended for the shrimp farms.