In February 1986, specimens of five massive sponge species (Pseudoceratina crassa, Ircinia felix, Verongula ardis, Smenospongia aurea and Agelas dispar) were collected from 20 m depth, approximately 1 km to the west of the Discovery Bay Marine Laboratory in Jamaica. The site was covered by a dense bed of Acropora rubble in excess of half a meter thick, which had accumulated during Hurricane Allen and contained numerous small sponges and coral colonies growing on pieces of the rubble.Regular-shaped animals (presumably derived from a single larva), which were attached to rubble and without obvious signs of predation damage were chosen. The sponges were weighed after draining for approximately 20 seconds and the volume measured by displacement in water. Estimates of dry weight were made on 5 individuals of each species after drying for 36 hours at 80°C.The size-class structure of the Pseudoceratina crassa population was estimated using the MIX program, which is an interactive program used to fit distributions to grouped data by maximum likelihood estimation. For Pseudoceratina crassa, it was assumed that there were five size groupings representing the recruitment from five annual spawning events between Hurricane Allen (August 1980) and the date of collection. The mean size of sponges in each size-class was determined from the significant fit obtained to the size-frequency data with the MIX program. These mean values for each size-class were analyzed using a least squares regression to provide an exponential growth model (Wt = ae^alpha t) from which the relative growth rate alpha was estimated.Growth rates for the other four sponge species could not be obtained by the same method due to the limited number of specimens. Growth rate approximations for these species were derived using the growth model from Pseudoceratina crassa, assuming that the average size at 50 days after spawning was the same for all species. Dates for spawning of these species were extracted from the literature.