Agonistic behaviour of male Anolis olssoni was elicited in natural habitats near Baraona, Barahona Province, Dominican Republic, through the introduction of tethered males. Videotaped responses consisted of various sequences and combinations of behaviours and modifiers and appeared to vary according to levels of arousal. Male A. olssoni assume a posture involving full head elevation and dewlap extension, which apparently signals the highest state of arousal to conspecifc males. This display was invariably accompanied by gaping with a protruded tongue, distinct extension of nuchal and dorsal crests, bulging eyes, and changes in body and tail colouration. Analysis of behaviours failed to identify a stereotypical display for this species. Males apparently monitor and defend their immediate surroundings, a strategy which may be adaptative in a densely occupied and complex microhabitat in which vision is restricted.