Chromosomal aberrations (CAs) in blood lymphocytes have been shown to be associated with overall cancer risk and aging. However, their relationship to bladder cancer risk remains to be elucidated. In a case-control study of bladder cancer in Egypt, we examined the relationship between the increased frequency of CAs in blood lymphocytes and bladder cancer risk. High frequency of CAs was significantly associated with an increased risk of bladder cancer [adjusted odds ratios (OR) = 3.90, 95% confidence interval (CI) = 2.65–5.73]. The associations were somewhat stronger in squamous cell carcinomas (SCC, OR = 4.90) than in urothelial carcinomas (UC, OR = 3.62). We also identified chromosome specific CAs for chromosomes 3, 4, 5, 8, 9, 10, 11, 12, 17, 19 that were significantly associated with an increased risk of bladder cancer. We observed particularly strong associations between aberrations