Renal allograft recipients are at an increased risk of neoplasia, although the extent of the problem has not been established in a typical European transplant population. To assess this risk we did a comprehensive, retrospective study of 918 patients transplanted at one centre over 24 years. The centre (Leeds) serves Yorkshire and Humberside, a region in northern England with a population of 3.6 million. The search, which made use of six sources of information, revealed 70 patients (7.6%) who had developed a neoplastic lesion, 10 patients having more than one type. More than half (42) were cutaneous lesions (mostly squamous cell carcinomas). The risk of developing neoplasia in the first 10 years after transplantation was calculated to be 14%. By 20 years this had risen to 40% compared with a 6% cumulative risk of neoplasia in an age-matched control population (p < 0.005). The full extent of this problem in the European transplant population has been underestimated and, now that recipients are surviving longer, there is a clear need for both lifelong surveillance and closer investigation of these patients.