Heavy metals are known or suspected to be hazardous for the marine environment; 13 of them are listed in the official list drawn up by the U.S. Environmental Protection Agency. In marine waters, lead is generally one of the most concentrated heavy metals; the main sources of lead input into the marine environment are rivers (domestic and industrial wastes) and atmosphere (mainly tetraethyl lead from automobile exhaust). Heavy metal toxicity for the marine environment is currently assessed by means of various biological tests based on different marine species. Among these, toxicity bioassays using sea urchin gametes and embryos appear to be quite sensitive and informative, offering a wide range of endpoints. Hence, sea urchin bioassays are now widely used in studies involved in the toxicological characterization of xenobiotics and in environmental monitoring. Some previous reports focused on different aspects of lead toxicity in sea urchin development; only Congiu et al. (1984) and Brunetti et al. (1991) investigated lead toxicity in Paracentroutus lividus. This sea urchin is widely distributed in the Mediterranean and European Atlantic coasts and is currently used in toxicological assessments. Its development was shown to be very sensitive to various heavy metals. In particular, Congiu et al. (1984)more » and Brunetti et al. (1991) reported that P. lividus development was sensitive to a lead concentration of 2.5 [times] 10[sup [minus]6]M (developmental retardation) and of 5 [times] 10[sup [minus]7]M (skeletal anomalies), respectively. The purpose of the present study was to extend available information on lead toxicity in P. lividus, by testing the effects on the fertilizing capacity of sperm and on offspring quality, as well as the effects on developing embryos. 19 refs., 1 fig., 3 tabs.« less