Altman and colleagues1 may well have underestimated the contribution of overweight and obesity to the increased incidence of renal cell cancer that they observed after hysterectomy. This is important in the absence of alternative plausible biological explanations for this finding. Obesity was unfortunately not analyzed in their study. They note some evidence for reduced rates of hysterectomy with obesity, presumably related to anticipated increased operative risk. However, overweight and obesity predispose to fibroids,2 uterine prolapse,3 endometrial polyps,3 and of course endometrial carcinoma, common indications for hysterectomy. Obesity has been consistently shown to predispose to renal cell carcinoma4,5 and, indeed, a large range of other neoplasms. However, if excess weight contributed to the increased renal cell carcinoma seen after hysterectomy, it is surprising that Altman and colleagues1 did not also find some evidence for an increase in other malignant neoplasms. That the association between obesity and malignancy appears to be strongest for renal cell carcinoma5 may be the reason why increased renal cell carcinoma stood out in the analysis by Altman and colleagues.1 Further studies may be required to clarify these issues.