The epidemic of obesity as measured by body mass index (BMI) maybe plateauing. However, studies using skin-fold and waist circumference measurements suggest that BMI may underestimate changes in fatness in children. In this study we examine changes in waist circumference and waist-to-height ratio (WHtR) in Australian children between 1985 and 2007, by undertaking secondary data analysis of three national data sets. The mean waist circumference z-score for boys increased from −0.02 (95% CI −0.05 to 0.01) in 1985, to 0.33 (0.26 to 0.40) in 1995 and 0.41 (0.35 to 0.47) in 2007 and was greater (P < 0.001) than the increase in BMI z-score. The increase in mean waist circumference z-score for girls was greater (P < 0.001) than boys and increased from −0.02 (0.05 to 0.01) in 1985, to 0.33 (0.26 to 0.41) in 1995 and to 0.57 (0.51 to 0.63) in 2007. The number of children with a WHtR ≥0.5 increased from 8.6% in 1985, to 13.6% in 1995 and 18.3% in 2007. Between 1985 and 2007 central adiposity increased at a faster rate than total adiposity, particularly in girls. The secular increase in waist circumference and WHtR is concerning as measures of central adiposity are associated with metabolic and cardiovascular risk.