Carp is one of the most widely cultivated warm water fish, which has been introduced into many countries. It is essential for the manager of a carp farm to know the production costs and their evolution, showing the main inputs on which the cost reduction is worth effort. In Iran, carp farming is mainly based on common carp, silver carp, grass carp, and bighead carp, which were often reared in poly culture. Carp farming production reached a peak in 2006 with production of more than 77,000 tones. The characteristics of the carp farming industry in the main fish farming provinces, (overall more than 90% of total carp production) are considerably different. In years 1996 and 2001, a study of yield production, factor costs and profitability of farmed carp was carried out to help clarify carp production costs and their difference between the provinces. 153 farms in 1996 and 101 farms in 2001, overall, a total of 254 farms from the main carp farming provinces, including; Guilan, Mazandaran and Khuzestan were randomly selected, classified and studied. Results showed that the various producer provinces have different cost structures. Overall, feed and fertilizer with the highest level of variation accounted for 45% of total costs in 1996, declined to 23% in 2001. However, on average, cost of seed and labor increased from 7% and 10% to 23% and 17% of total costs over the 1996 and 2001, respectively. On average, benefit-cost ratio and the rate of farm income were closely related to location suggesting that farmers practiced more efficiently and have better conditions in Guilan in 1996, resulting in higher farm income per ha and per kg, changing to better conditions and more efficient by Mazandaran province in 2001. Overall, in the three main provinces, rate of farm income from an average of 20% in 1996, declined to 12% in 2001.