Prolonged exposure of a limited size range of sea scallops ( Placopecten magellanicus) to undiluted mineral oil-based drilling mud (OBM) cuttings from two sources resulted in: increased mortalities, cessation of reproductive and somatic tissue growth, decreased body component condition indices, and failure to accumulate lipid reserves. Exposure of sea scallops to concentrated mineral OBM cuttings has potentially damaging implications for production, reproductive success and population survival in the vicinity of a drilling platform. Estimates of the extent and duration of impact zones around a drilling rig employing mineral OBM (either exploratory or production) are necessary to resolve potential conflicts between the petroleum and fishing industries.