The existence of a link between the thermogenic capacity and the basal rate of metabolism (BMR) in mammals is still a matter of controversy. However, the question is important because of its evolutionary and ecological implications. The relationship between thermogenic capacity (estimated by both summit metabolism V̇o_{2 sum} and maximal nonshivering thermogenesis [NST_max]) and BMR was examined in shrews by comparing values obtained in 12 species from temperate and tropical climates. The analysis was carried out with methods that account for the phylogenetic relationship among species. Measured V̇o_{2 sum} was higher in temperate species, regardless of their BMR level. This resulted in a greatly improved cold tolerance; on the average there was a 20° C difference between temperate and tropical species in the lower lethal ambient temperature. The NST_max values were not different between the climatic groups, and they were close to the expected values. The analysis of these results suggests that the level of BMR and the thermogenic capacity are not correlated; therefore thermoregulatory needs cannot explain the high BMRs observed in shrews. The generality of this conclusion and its implications for a theory on the evolution of homeothermy in mammals are discussed.