Age and growth of Nile tilapia (Oreochromis niloticus) were determined using 1039 specimens collected in a tropical shallow lake of Mexico, from January to December 1993. Standard length of females ranged from 9.0 to 16.5 cm and males from 8.9 to 14.8 cm. The standard length-weight relationships for all individuals was BW=0.1207 SL2469. The age data, derived from opercular bone readings, were used to estimate the growth parameters of the von Bertalanffy equation: Lx=17.88 cm, K=0.3409, t0=-1.543, and Winfinity=149.21 g. The oldest male and female were 2.5 years old. The sex ratio (female:male) was of 1:1 (chi2=0.02, p>0.05).