Little is known of the current status of platypus (Ornithorhynchus anatinus) populations in the Murrumbidgee catchment and other west-flowing rivers in the Murray-Darling Basin. Platypus distribution in the Murrumbidgee catchment was determined from sightings, reports by government departments, the literature and a capture-release study. The platypus was found to be widespread in the catchment including all subcatchment and elevation categories, but most reports were from the middle and upper sub-catchments. Sixty-five captures of fifty-five individual platypuses were made during 61 trap nights to 31 study sites in the Murrumbidgee catchment from 2009-2010. Only three juveniles (all females) were captured and recapture rates were low, with only nine platypuses captured more than once. Adult males had body weights of 980 to 2180 g and body lengths of 42 to 60 cm (n=32). Adult females weighed 795 to 1480 g and were 38 to 52 cm long (n=20). Tail fat index was significantly effected by season and platypus age, while in comparison, season, platypus length and weight had a significant effect on tail volume index. This study established a baseline that provides a starting point from which the impacts of environmental disturbances or diseases taking place over time can be measured and investigated.