Penaeid prawn,Penaeus indicus (H Milne Edwards), was subjected to acute (2 day) and chronic (15 day) exposure to sublethal concentration (0·2 ppm) of phosphamidon, and changes in the carbohydrate metabolism of phasic and tonic muscles were investigated. Differential patterns in carbohydrate metabolism were witnessed. The glycogen content of phasic muscle was elevated, whereas that of tonic muscle was depleted in response to acute exposure. During chronic exposure, both muscle tissues had elevated glycogen content. In general, both phasic and tonic muscles exhibited low-level of glycolysis and elevated oxidative pathway operation, leading to elevated glycogen content. Both, phasic and tonic muscle metabolisms were oriented towards conservation of carbohydrates and lesser production of organic acids during chronic exposure, as a possible adaptive metabolic mechanism of this prawn enabling it to counteract the toxic stress imposed by phosphamidon.