The defensive behavior of the endemic tropidurid lizard Tropidurus montanus was studied from January to March 2004 at the Serra do Cipó, State of Minas Gerais, southeastern Brazil. This lizards relied on crypsis associated with immobility as the primary strategy of defense to avoid predators. When attacked, locomotor escape was the tactic employed by all recorded individuals. We analyzed the effects of sex on the maximum flight distance and the effects of body size and social context on maximum flight distance and time of flight for males. Males and females did not differ in maximum flight distance. Males with or without a nearby neighbor did not differ in maximum flight distance, but males close to neighbors increased time spent in flight. We found no effect of male body size on maximum flight distance or on the duration of flight. During capture, lizards exhibited threat display, bite, tail waving, tail breakage, thanatosis, forced freeing, body inflation, and cloacal discharge.