Metabolic costs of resting and locomotion have been used to gain novel insights into the behavioral ecology and evolution of a wide range of primates; however, most previous studies have not considered gait-specific effects. Here, metabolic costs of ring-tailed lemurs (Lemur catta) walking, cantering and galloping are used to test for gait-specific effects and a potential correspondence between costs and preferred speeds. Metabolic costs, including the net cost of locomotion (COL) and net cost of transport (COT), change as a curvilinear function of walking speed and (at least provisionally) as a linear function of cantering and galloping speeds. The baseline quantity used to calculate net costs had a significant effect on the magnitude of speed-specific estimates of COL and COT, especially for walking. This is because non-locomotor metabolism constitutes a substantial fraction (41–61%, on average) of gross metabolic rate at slow speeds. The slope-based estimate of the COT was 5.26 J kg−1 m−1 for all gaits and speeds, while the gait-specific estimates differed between walking (0.5 m s−1: 6.69 J kg−1 m−1) and cantering/galloping (2.0 m s−1: 5.61 J kg−1 m−1). During laboratory-based overground locomotion, ring-tailed lemurs preferred to walk at ∼0.5 m s−1 and canter/gallop at ∼2.0 m s−1, with the preferred walking speed corresponding well to the COT minima. Compared with birds and other mammals, ring-tailed lemurs are relatively economical in walking, cantering, and galloping. These results support the view that energetic optima are an important movement criterion for locomotion in ring-tailed lemurs, and other terrestrial animals. Am J Phys Anthropol, 2012. © 2012 Wiley Periodicals, Inc.