In the present study, age, growth and reproduction of Carassius auratus were investigated in the Alma-Gol and Ala-Gol (northern Iran) from September 2000 to August 2002. Among the total of 1450 specimens, the estimated ages ranged from 0+ to 8+ years. C. auratus showed an allometric growth, negatively in Alma-Gol and positively in Ala-Gol. The von Bertalanffy growth curves were fitted to mean total lengths at age, resulted as Ltmales=183.33(1-e-0.31(t+1.05)) and Ltfemale=245.66(1-e-0.19(t+1.21)) for Alma-Gol population and Ltmale=224.79(1-e-0.24(t+0.83)) and Ltfemale=242.80(1-e-0.23(t+0.80)) for Ala-Gol population. The value of f’ index varied from 9.25 to 9.51. The unbalanced sex ratio of males to females was 1:10 and 1:12.7 in Alma-Gol and Ala-Gol, respectively. The reproductive period for this species in these particular areas was February, March and April and the maximum recorded GSI was 2.19 and 2.17 for males and 10.37 and 10.49 for females in Alma-Gol and Ala-Gol, respectively. The linear relationship between absolute fecundity and total weight was more suitable for expressing the fecundity-weight relationship for both populations as estimated: Fec.Alma-Gol= 4120.56+ 62.62W and Fec.Ala-Gol= 3832.83+ 68.67W.