Freshwater crocodiles Crocodylus johnstoni were observed aestivating in dry caverns in the undercut banks of Saunders Creek in the Northern Territory during each dry season over a period o f six years. During most years at the site there were both crocodiles that had been marked in previous years and unmarked individuals. Aestivating crocodiles ranged in mass from 0.95 kg to 42.0 kg , but the smaller size classes were under-represented compared to a population living in permanent water in the nearby McKinlay River region. The nesting season of freshwater crocodiles coincides with the period during which the crocodiles entered aestivation (late August to early September) , and there was no evidence that the crocodiles at the aestivation site nested. Apart from this disadvantage, there was no evidence that aestivation was detrimental. Growth rates and body condition of aestivating crocodiles were not markedly different from crocodiles that inhabit the permanent water of the McKinlay River region. Aestivation in response to seasonal drying is clearly a regular, probably annual, feature in the life history of the freshwater crocodiles inhabiting Saunders Creek, and it may be widespread among crocodiles living in seasonally intermittent creeks in northern Australia.