The biology of the tub gurnard, Chelidonichthys lucernus (Linnaeus, 1758). has been studied on data collected between November 1996 and November 1997 from the Sea of Marmara. Totally, 224 tub gurnards were sampled. The age, growth, length-weight relationship, condition factor, male to female ratio, first sexual maturity age, length and reproduction period were examined. The age composition of samples ranged between I and 6 years. Total length ranged between 12.3 and 41.5 cm, while weight varied from 15 to 617 g. The total length-weight relationship was estimated as W = 0.0092L(3.019). The parameters of the von Bertalanffy growth equation were: L(infinity) = 61.3 cm, K = 0.17 year(-1), to = -0.04 year. The observed sex ratio was 1 female: 0.5 male in the samples. The lengths and ages at first maturity (L(T50)) for tub gurnard were 18.97 cm and 3 years for females, 18.50 cm and 3 years for males. Possibly, reproduction is achieved throughout the year.