Aim of the study: To examine risk factors for developing hypertension in childhood cancer survivors (CCS). Methods: We conducted a nested case-control study of risk for hypertension within a cohort of 1362 childhood cancer survivors treated between 1966 and 1996 in the Emma's Children's Hospital/Academic Medical Center in the Netherlands. Detailed information on treatment and several lifestyle factors was collected for 44 cases with hypertension and 123 matched controls. Odds ratios (ORs) for hypertension were calculated by conditional logistic regression analysis. Results: Body Mass Index (BMI) was the only significant risk factor associated with the occurrence of hypertension (OR 3.95; 95% confidence interval (CI) 1.7-9.1 for BMI ≥ 25 kg/m2 compared to BMI < 25 kg/m2). However, cisplatin, cyclophosphamide and radiotherapy (RT) to the abdominal region were all associated with non-significant risk increases (ORs of 4.3, 2.1, and 1.8, respectively). Conclusion: Our results show that BMI is the most important risk factor for hypertension following treatment of childhood cancer, emphasising the need for CCS to maintain a normal weight.