Individuals of Eucidaris tribuloides (Lamarck) were held at 18 and 27°C and fed either a low or high quality diet (1 or 10% fish meal in agar) to ascertain the effects of food quality and temperature on rates of feeding, absorption of nutrients, and gut passage time. Sea urchins fed a low quality diet had significantly higher rates of feeding and fecal production than sea urchins fed a high quality diet at either temperature. Individuals fed a low quality diet had significantly higher nutritive absorption efficiencies (99.4% at 18°C, 95.2% at 27°C) than individuals fed a high quality diet (87.6% at 18°C, 89.5% at 27°C). The absorption of nutrients (mg) and energy (kJ) from the food were significantly higher for individuals fed a low quality diet than individuals fed a high quality diet. Gut passage times of individuals held under the four treatments were not significantly different. These results indicate that E. tribuloides responds to low quality food by increasing feeding rates and absorption efficiency, without adjusting gut passage time. Temperature does not affect this response to food quality. © 1991.