Length distribution, sex ratio, length-weight relationship, age, growth, spawning period, age, and length at first maturity of four-spotted goby inhabiting Izmir Bay were investigated. A total of 1696 four-spotted goby were collected by trawl hauls between July 2004 and June 2007. The size of the fish sampled ranged from 3.1 to 9.2 cm total length. The samples were composed of 31.1% females, 27.7% males, and 41.2% juvenile individuals, with a female to male ratio of 1:0.89. The age of the fish ranged from 1 to 5 years. The length-weight relationship and the von Bertalanffy growth function were estimated for all individuals as: W = 0.0036L(3.45) and L-t = 10.29[1 - e(-0.37t(t + 0.502))]. Spawning period started in February and continued until May. The lengths at first maturity of females and males were 6.15 +/- 0.18 and 6.38 +/- 0.20 cm total length, respectively.