Abstract: A four month long experiment was conducted in earthen ponds (each of 81 m² in size) during the month from August to November, 2001 to observe suitable stocking density of Macrobrachium rosenbergii in polyculture of Indian major carps viz. catla (Catla catla), ruhu (Labeo rohita) and mrigal (Cirrhinus mrigala). Six densities of M. rosenbergii with carps were considered as treatments. Each treatment had three replications. All the fish were same age group and mean initial weight of prawn, catla, ruhu and mrigal were 1.1± 0.12, 14.2 ± 0.52, 8.5 ± 0.16 and 11.8 ± 0.20g respectively. Water quality parameters including temperature, dissolved oxygen and pH were found in the suitable range. The best combination of prawn-carp polyculture (prawn: catla: ruhu: mrigal = 25: 15: 15: 15) was found in the treatment T₃ with significantly (p<0.05) highest growth of M. rosenbergii and carps.