Despite high numbers of cats admitted to animal shelters annually, there is surprisingly little information available about the characteristics of these cats. In this study, we examined 195,387 admissions to 33 Australian RSPCA shelters and six friends of the RSPCA groups from July 2006 to June 2010. The aims of this study were to describe the numbers and characteristics of cats entering Australian RSPCA shelters, and to describe reasons for cat surrender. Data collected included shelter, state, admission source, age, gender, date of arrival, color, breed, reproductive status (sterilized or not prior to admission), feral status and surrender reason (if applicable). Most admissions were presented by members of the general public, as either stray animals or owner-surrenders, and more kittens were admitted than adults. Owner-related reasons were most commonly given for surrendering a cat to a shelter. The most frequently cited owner-related reason was accommodation (i.e., cats were not allowed). Importantly, although the percentage of admissions where the cat was previously sterilized (36%) was the highest of any shelter study reported to date, this was still lower than expected, particularly among owner-surrendered cats (47%). The percentage of admissions where the cat was previously sterilized was low even in jurisdictions that require mandatory sterilization.