To investigate whether overweight women are more likely to have a hysterectomy and whether hysterectomy leads to increased weight gain.Survey data of middle-aged women participating in the Australian Longitudinal Study on Women's health in 1996 (ages 45-50 y; n = 13,125), 1998 (n = 10,612), 2001 (n = 10,293), and 2004 (n = 9309) included self-reported height, weight, and hysterectomy. First, we conducted a cohort analysis, comparing body mass index (BMI) of women categorized according to hysterectomy status. Second, we used a nested case-control analysis to compare weight gain between women who underwent hysterectomy and women who did not have a hysterectomy, matched for prehysterectomy weight, height, menopause status, and educational level.At survey 1, the mean BMI of women who subsequently had a hysterectomy was greater than that of women without a hysterectomy by survey 2 (difference, 1.1 kg/m; 95% CI, 0.5-1.6). Results were similar for surveys 2 to 3 (BMI difference, 0.8 kg/m; 95% CI, 0.3-1.3) and surveys 3 to 4 (BMI difference, 0.8 kg/m; 95% CI, 0.1-1.4). Having a hysterectomy between surveys 1 and 2 was not associated with percentage of weight gain over the 3 or 6 years after survey 2 (odds ratio, 0.98 [95% CI, 0.96-1.01] and 0.99 [95% CI, 0.97-1.01], respectively). Having a hysterectomy between surveys 2 and 3 was weakly associated with percentage of weight gain over 3 years (odds ratio, 1.03 [95% CI, 1.00-1.05]).Among women older than 45 to 50 years, hysterectomy did not lead to greater weight gain but was more likely to be performed in heavier women.