This study describes temporal variations of early larval stages of the long-spined sea urchin, Diadema antillarum in neritic waters of La Parguera, Puerto Rico. Larvae were sampled with oblique plankton tows between the new and full moons at monthly interval from April 2005 to July 2006, and September 2006. Early pluteus stages (< 5 days old) were found in 13 out of the 16 months of sampling, indicating that Diadema spawns throughout the year. Mean abundances were significantly higher during April and July 2005 compared to the other months, suggesting higher reproductive activity during these months. Larval abundances were variable between years and successive months possibly reflecting a patchy distribution of larvae. Drogues released during the April spawning season from an area of high aggregations of mature adults indicated that a neritic, topographically steered flow fringing the inner shelf forereef platforms confined the early larval stages of Diadema within the insular shelf of La Parguera.