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The diets of five syntopic species of Ctenotus were examined over a two-year period on a 60 ha spinifex grassland site in central Australia. The aims of the study were to test predictions that termites were an important part of the food web for syntopic Ctenotus in spinifex grasslands, and to examine seasonal changes in prey use and dietary overlap between the species. Environmental conditions during the first season of the study were dry resulting in generally low invertebrate abundance. In contrast the second season was relatively moist and overall invertebrate abundance was higher than in the first season. Diets of five species of Ctenotus contained a range of terrestrial prey although one species (C. pantherinus) was relatively termite-specialized at all times. Dietary overlap at the ordinal level between the species was generally higher during dry periods when prey abundance was low, and higher for species-pairs that were similar in body size. During the driest period of the study most species of Ctenotus ate a high proportion of termite prey which accounted for the high dietary overlap. However, each species of Ctenotus consumed different genera or foraging guilds of termites. The results suggest that most of these lizards were opportunistic in their selection of prey but that during dry periods when prey are scarce, termites may play a significant role in supporting a high alpha-diversity of Ctenotus.