The toxicity of chlorine to juvenile chinook salmon (Oncorhynchus tshawytscha) was tested at five residual concentrations ranging from 0.05 to 1.0 mg/liter and at four temperatures (Δt 0, 2.6, 4.9, and 10 C) in a matrix design. Juvenile pink salmon (O. gorbuscha) were tested at three temperatures (Δt 0, 5.0, and 9.9 C). Each matrix was stressed at four exposure periods (7.5, 15, 30 and 60 min). An array of LC50 and LT50 values are presented for each of the conditions tested. A decrease in the tolerance of both species to residual chlorine was demonstrated with increasing temperature and exposure time. The 60-min exposure period and the 9.9 and 10 C Δt were the most acutely toxic to each species. The equilibrium loss response for chinook salmon exposed to heat and chlorine preceded the LT50 by at least 55%. The LC50 was 0.045 mg/liter for both species after exposure to fluctuating chlorine concentrations during 2-hr periods. The LT50 occurred in about 100 min at approximately 0.5 mg/liter residual chlorine.