Reports suggest that 7% to 18% of Australian adults are obese and a further 16% to 55% are overweight. Studies from other countries have indicated that obesity among people with an intellectual disability may be at least, or even more, prevalent. Prevalence rates range from 28% to 59%. The aim of the current study was to investigate the weight distribution of an Australian sample of people with an intellectual disability using Body Mass Index (BMI) to classify males and females, and Kelly and Rimmer's (1987) Percentage of Body Fat (PBF) formula to also classify males. Forty-one females and 52 males with a mild to severe intellectual disability were assessed. The correlation between BMI and PBF for males was r =.89. BMI classifications revealed a higher percentage of females as overweight (41.4%) and obese (36.6%) compared to overweight males (30.8%) and obese males (30.8%). There were more underweight males (7.6%) than females (4.9%). There was no relationship between living environment and weight classifications on the BMI. The PBF formula indicated that 73% of the males were classified as obese. The possibility of misclassification using the BMI and the need for weight interventions are discussed.