The hyperglycemic stress response of fish was evaluated for use as a rapid test for assessing stressful levels of pulpmill effluents (BKME). Plasma glucose levels in juvenile coho salmon (Oncorhynchus kisutch) were elevated within 0.5 h following transfer from the holding tank to aquaria containing either fresh water or BKME, peaking at 3–6 h and returning to near-basal levels at 24 h. Acclimation of coho to aquaria for 24, 48, 72, or 96 h prior to addition of effluent resulted in marked increases in glucose levels attributable to BKME. Significant responses to effluent were found with exposures of 3–10 h, whereas levels were not increased with exposures of 2 h or less. Plasma glucose levels increased progressively with increasing effluent concentrations. Threshold effect (EC50) values varied from 0.04 to 0.16 of the 96-h LC50 values. The response to BKME treated previously by the activated sludge process or by foam separation was diminished or absent altogether.Juvenile rainbow trout (Salmo gairdneri) and coho displayed a hyperglycemic response with 4-, 6-, or 8-h exposure to an identical effluent concentration, although the magnitude of response of rainbow was less in each instance.The extent to which blood sugar levels are elevated due to effluent exposure is directly related to the liver glycogen reserves of the fish. Acclimation to test tanks for 24–48 h followed by exposure for 3–6 h is suggested as the best working combination for this test.