The metabolic cost of stress increased with the severity of handling in juvenile coho salmonOncorhynchus kisutchexamined via respirometry. Stressed fish had rates of oxygen consumption 39–98% higher than controls. Elevation in oxygen consumption was largely eliminated within 1 h after stress. Oxygen consumption was significantly correlated to both plasma cortisol and lactate concentration in response to a moderate stressor, but no correlation was found after more severe stressors. Fish given exogenous cortisol did not experience an increase in oxygen consumption, so cortisol alone is unlikely to have a major effect on metabolic rate. Whole-body lactate concentration was significantly elevated following stress, reaching levels almost 500% higher than controls. We suggest that metabolism associated with exercise or hypoxia is the dominant source of elevated oxygen consumption following handling.