In Mar del Plata the octocoral Tripalea clavaria is highly abundant on the different quartzitic rocky outcrops 18–20 m deep. Reproductive aspects of T. clavaria including its distribution and population structure have been described. Monthly sampling and observations were carried out by SCUBA diving from November 2000 to October 2001 at Banco del Medio (38°10′S 57°28′W). Tripalea clavaria occurs in patches; most colonies were 3·0–8·9 cm in height. The species appears to be a gonochoric brooder. Female colonies were significantly more abundant than males, which could be identified only from February to June, when spermaries were present. Oocytes were found even in very small colonies (from 3·5 cm height), being 40 to 200 μm in diameter, the predominant size-group around the year. Development of the oocytes required several months, beginning in May and ending with the production of larvae from March to May. Young, stalked oocytes were found at the base of the polyps attached to the mesenteries in May–June. During the following six months they grew in size; maximal oocyte diameter was 700 μm, observed in April/May. Asexual reproduction was negligible, indicating that population maintenance is based on sexual reproduction.