Bobwhite quail were exposed to 2,4-dinitrophenol (DNP) in a respirometer designed to continuously monitor exchange of O2 and CO2, from which metabolic rates (MR) were estimated. After 14-16 days of acclimation to the system (temperature 22 deg C, light cycle 8L:14D), hens received feed amended with 0, 625 ppm, or 1250 ppm DNP ad libitum for eight days, followed by 2-5 days of 0 ppm feed. The 625 ppm treatment produced dark period MR 31-41% higher than corresponding control values, and light period MR 23-32% higher than controls. The 1250 ppm treatment produced dark period MR 48-77% higher than control values, and light period MR 41-67% higher than control. Over the eight days of testing, the 625 ppm treatment hens expended 32% more energy than the control hens and hens consuming 1250 ppm feed expended 60% more energy than control hens and lost most of their body fat. In general, the risk of being unable to meet energy demands for survival or reproduction would probably be substantially increased by the observed elevation in MR. (Copyright (c) Toxicology and Applied Pharmacology 1993.)