1. 1. Panterpe insignis and Eugenes fulgens, highland tropical humming-birds, regulate body temperature in torpor at 10–12°C through an increase in oxygen consumption below ambient temperatures of 10–12°C. 2. 2. The rate of increase of oxygen consumption for both species in torpor and at rest were not significantly different. 3. 3. From ambient temperatures of 27-12°C the birds usually maintained body temperatures that slightly exceeded ambient temperatures. 4. 4. Regulation of body temperature in torpor has also been reported for two other species of hummingbirds, Eulampis jugularis and Oreotrochilus estella. 5. 5. The regulation of body temperature in torpor for these four species is related to minimum environmental temperatures and is not a function of body size.