The reactions of a territorial male lizard (Anolis aeneus) to an intruder were filmed and analyzed. Five displays were given to the intruder: Fanbob, Multibob, Jerkbob, Gorged-throat and Fan. Fanbob consists of the species-specific signature bob and dewlap extension and is the normal display given as a challenge to intruders. Multibob, another bob pattern, occurs when a degree of anxiety is present. It closely resembles the Courtship Bob, so the male is in effect giving an appeasement display while courting a female. Jerkbob is used as an introductory display preceding Fanbob during territorial advertisement. Gorged-throat is a threat display, and Fan may be used instead of Fanbob when inhibitory factors prevent Fanbob from being expressed. Fanbob was analyzed to test whether it fulfills the criteria of the Fixed Action Pattern. The cadence of the signature bob was individual-specific and stereotyped, but other components of Fanbob varied greatly. Among these were presence and absence of introductory movements (related to intruder distance), degree of sideflattening and degree of dewlap extension (related to resident aggressiveness), and height of head during the display. Height and dewlap extension, while necessary and integral components of Fanbob, varied independently, and were correlated with different sets of stimulus and response variables. Fanbob was thus shown to fit none of the criteria of a fixed action pattern.