The combined influence of temperature and food concentration on Pteria sterna growth was determined, using 3 temperatures and 3 food concentrations. During 15 wk, the shell was measured weekly along the axis of maximum growth. The 2 higher growth rates (4.8 and 4.2 mm mo-') were obtained with the highest ration, at 30 and 25 'C, while with the lowest food concentration growth was not temperature dependent. By the response surface analysis, a synergistic effect of temperature and food concentration on growth was found. Food concentration, but not temperature, had an important influence on condition index (ash free meat dry weight/shell dry weight X 100).