Various studies indicate the acmaeid limpet species Collisella digitalis, Collisella pelta and Notoacmea scutum inhabit different vertical zones in the rocky-intertidal region. At Sunset Bay, Oregon, Shotwell (1950) found that C. digitalis was situated in the upper intertidal C. pelta inhabited the mid-intertidal and N. scutum was located in the mid to lower zone in the rocky-intertidal region. Frank (1965) observed the same distribution patterns at Coos Bay, Oregon as did the author in the rocky-intertidal region near Dillon Beach, California. Species distributions in the rocky-intertidal region are thought to be limited from above by physical stress and from below by predation or competition (Connell 1970; Dayton 1971; Vermeij 1972; Paine 1974; Bertness 1977). The purpose of the present study was to investigate effects of the predators Pisaster ochraceus, Cancer antennarius and Pachygrapsus crassipes on the distributions of the three acmaeid limpet species particularly with respect to their lower limits.