An ethogram of the blue spiny lizard, Sceloporus cyanogenys, was derived from laboratory studies of feral populations in various enclosures designed to maximize the expression of behavior patterns by providing a diversity of natural and semi-natural environ- mental cues. A behavior inventory enumerating and defining 76 distinctive postures, orienta- tions, and simple movements is presented and then inventory units are grouped into functional categories for discussion. Thermoregulatory behavior was divided into basking and thermal comfort patterns. Perching behavior was characterized by distinctive postures which suggested a readiness to act rapidly. Both perching and basking behavior took place not only at exposed sites but also within a shelter or at its inner threshold. Predatory behavior consisted of two distinct strategies: perch feeding in which lizards fed opportunistically on moving prey, and foraging, in which lizards would move in the environment investigating non-moving potential prey. Feeding was generally inertial but supplemented with shaking and scraping movements when a lizard was contending with large prey. Courtship behavior and mating were typical of iguanid lizards but courtship included an unusual tail-grip restraint by a male of a retreating female. Assertive and aggressive displays could be distinguished by both form and context.