The reproduction of Aphanius mento is described from the Kirkgoz Spring (Turkey) (37 degrees 06' N; 30 degrees 35 E) between January 2002 and December 2002. In this study, the sex ratio, age, the relationship between fecundity and fish length, weight and gonad weight, the gonadosomatic index, egg diameter and the first age of maturation were observed. Age range was determined as 0-VII years for 654 individuals. The overall male to female ratio was 1.10 : 1.00. Spawning period was between May and July. The first maturation was found to be at age I. First maturity length (L-m) was estimated at 2.45 cm for females. The mean fecundity per individual was found to be 228.48 +/- 28.60. The mean egg diameter was calculated as 1,240.09 +/- 53.26 mu m.