Bay scallops from Homosassa, FL, were spawned at the Department of Marine Science, University of South Florida at St. Petersburg, FL. Total dry weight (DW) and ash free dry weight (AFDW) were determined for larvae and juveniles. DW and AFDW (in milligrams) increased with increasing shell length (L, in millimeters, for larvae) or shell height (H, in millimeters, for juveniles), according to the following allometric equations: DW = 0.0693L-2.715 and AFDW = 0.0459L-2.984 in larvae and DW = 0.0715H-3.069 and AFDW = 0.0138H-2.664 in juveniles. Growth was determined for larvae and juveniles at 25 degree C under six algal concentrations of Isochrysis galbana (1-30 cells/mu-L for larvae and 1-50 cells/mu-L for juveniles). Growth rates increased as algal concentration increased. The maximum larval growth rate ranged from 7-23 mu-m/day. The development of eyespots and metamorphosis started earlier at higher algal concentrations. The optimal algal concentration for growth was 20 cells/mu-L for larvae and 10 cells/mu-L for juveniles. In juveniles, the growth rate was higher and increased with increasing body size. The relative growth rate (daily percent increase in AFDW) was higher in larvae than in juveniles and decreased with increasing body size in juveniles.