The incidence of malignancy in transplant recipients is known to be higher than the same in the general population. However, the types of malignancies vary geographically, and the relative risks (RR) for malignancy in transplant recipients, compared with that of the general population, also differ country-by-country. In this study, we investigated the incidence and characteristics of malignancies after renal transplantation in a single center. A total of 2630 renal recipients who underwent surgery between April 1979 and June 2007 were enrolled in this study. The cumulative and interval incidences of malignancies were calculated for every 3 years post-transplantation. One-hundred ninety cases of postrenal transplant malignancies among 177 recipients (6.73%) were reported until 2007. The post-transplant malignancies were detected from 6 to 290 months after transplantation, with a mean duration of 112.6 +/- 66.0 months. Skin cancer [35 (18.4%)] was the most common post-transplant malignancy, followed by thyroid [25 (13.2%)], stomach [22 (11.6%)], colorectal [22 (11.6%)], and urologic cancers [19 (10.0%)]. As the post-transplant period increased, the interval incidence of malignancy correspondingly increased. Virus-related malignancies, such as Kaposi's sarcoma and cervical cancer, developed earlier within the post-transplant period, while urologic cancer, colorectal cancer developed late in the post-transplant period. The recipient's age at the time of transplantation was the sole independent risk factor for post-transplant malignancy based on the multivariate analysis (RR = 2.723, P < 0.0001 in the >50-year-old age group). We should establish strategies for post-transplant malignancy-screening based on the recipient's age at the time of transplantation, the post-transplant interval, and the national trend of post-transplant malignancy.