One hundred eleven active and 71 standard metabolic rate estimates were made on 90-g cutthroat trout Salmo clarki at five temperatures. Active metabolism was lowest at 5 C (363 mg O2kg-h) and highest at 15 C (597 mg O2kg-h). At 20 C and 24 C it was 559 and 491 mg/kg-h, respectively. Scope for activity ranged from a low of 316 mg O2kg-h at 5 C to a high of 486 mg O2kg-h at 15 C then down to 374 mg O2kg-h at 24 C. Standard metabolisms at 5, 10, 15, 20, and 24 C were 47, 73, 111, 129, and 117 mg O2kg-h respectively.