We examined whether Australian varanids as a group are more aerobic than other lizards. The standard metabolic rate (SMR) and maximal oxygen consumption (V02max) were measured for four species of varanid lizards and the skink Tiliqua rugosa at 35°C. These were compared to each other and to the Vo2maxax °f the iguanid lizard Cyclura nubila by analysis of covariance with body mass as a covariate. There were no differences with respect to SMR, but the Vo2max of the lizards fell into three groups: Varanus rosenbergi, V. gouldii and V. panoptes had higher aerobic capacities than V. mertensi and Cyclura nubila, and Tiliqua rugosa had a Vo2max lower than the other species. There is no simple relationship between Vo2max and the time these lizards spend in natural activity. The summer SMRs of V. rosenbergi and T. rugosa were significantly higher than during other seasons. The Vo2max of V. rosenbergi was higher in summer than in other seasons, but T. rugosa showed no seasonal differences in Vo2max. These results indicate that the SMRs of the varanids were similar to those of other lizards, and, despite generalisations in the literature, not all varanid lizards have high aerobic capacities. Varanid lizards may be as physiologically diverse as other lizard families. © 1994 CSIRO.