Vertebral quality of fourhorn sculpin (Myoxocephalus quadricornis) exposed to pulp mill or ore smelter effluents was investigated in the laboratory and in contaminated sites near the Swedish coast of the Gulf of Bothnia. Actual effluent samples from pine and birch pulp processes (chlorine bleaching) and a simulated effluent of the ore smelter effluent were tested in the laboratory. In the field, fish were collected from both reference (control) and contaminated sites. Laboratory exposures of pulp mill effluent significantly affected biochemical composition of vertebrae, but no statistically significant effects were observed in fish from the field. Mechanical properties were significantly affected in fish from both the laboratory and field; spinal anomalies ranged from 19 to 38%. Major effects on mechanical properties of vertebrae were observed in the ore smelter study, but the properties affected in laboratory fish differed from those affected in the field. Incidence of spinal anomalies was 47 to 58% in the laboratory and 29% in the field. Effects on fish in the laboratory were related to those observed in the field for pulp mill effluents, but the stimulated effluent for the ore smelter elicited vertebral responses different from those in fish exposed to actual effluents in the field. (Copyright (c) American Society for Testing and Materials, 1988.)