A relationship between total lengths and body depths of certain fish larvae was used to predict the effectiveness of small-mesh screens in limiting entrainment of fish larvae at cooling-water intakes. Total length-body depth regressions were linear for eight species (293 larvae) common to Lake Michigan near the J. H. Campbell Power Plant at Port Sheldon, Michigan. Regressions indicated that 35–100% (depending on species) of the fish larvae that had been entrained by the J. H. Campbell Plant in 1978 would have been excluded if 0.5-mm mesh screening had been employed in the plant's cooling water intake system instead of 9.5-mm bar mesh vertical traveling screens. These calculations do not take into consideration approach velocities of intake water, larva avoidance behavior, or mortality due to impingement on or extrusion through the screens.