The effects of water temperature and light regimes on gonadal development in the sea urchin Paracentrotus lividus were evaluated in two 12-week periods, one in spring-summer and one in winter-spring. Four different combinations of photoperiod and temperature regimes (18-26 o C) were tested in each. Sea urchins were fed a prepared diet. Food intake, growth, gonadosomatic index, biochemical composition and gametogenetic stages were measured. Results show that water temperatures between 18 and 22 o C enhance growth and gonadal development. Long days (illumination) reduce the rates of gametogenesis while short days increase reproductive development.