Pentaporafascialis, one of the largest living bryozoan, is often a predominant part of the benthos on hard subtidal bottoms in the Mediterranean Sea. Conversion factors calculated from laboratory measurements of colony size, biomass and skeleton weight, combined with density of colonies and mean annual growth rate allowed the estimation of carbonate standing stock, biomass and carbonate production of Pentapora fascialis in five sites in the Ligurian Sea. Carbonate standing stock ranged from 281 to 2490 g.m(-2), colony biomass varied from 8.82 to 78.01 g.m(-2). with a ratio biomass to carbonate standing stock of about 3%. Carbonate production of the bryozoan ranged in the five sites from 358 to 1214 g.m(-2).y(-1). If compared with the few data available on carbonate production of bryozoans and other sublittoral benthic bioconstructors in the temperate regions, Pentapora fascialis has to be considered one of the major contributors to the carbonatebudget.