Overweight and obesity continue to contribute to increased risk of chronic diseases, including higher lifetime health expenditures and impacting on individualsÂ’ quality of life. Whilst international studies have compared individualsÂ’ perceptions of their body mass with more objective measures such as Body Mass Index (BMI) few Australian studies have examined this relationship in any detail. This study uses unit record data from the 2003 NSW Health Survey to identify factors associated with the accuracy of adults perceived body mass. Descriptive methods and logistical models are used to quantify the effects of a number of demographic, socioÂ–economic, behavioural and healthÂ–related variables on the accuracy of selfÂ–assessed body mass. The results support earlier findings that there are large gender differences in perception of body mass. Women are most likely to report they are overweight. In contrast there is a pattern of underestimation of weight amongst men, particularly at the higher BMI deciles. Clearly these results have different policy implications. This information may be useful for public health programs to take into account the issue of whether individuals accurately perceive themselves at risk of developing weightÂ–related health conditions.