Patients with prostate cancer are at a significant risk of either having a preceding tumour or developing a second malignancy. The precise mechanism by which second cancers develop is not clear but may be the result of exposure to a shared mutagen, abnormalities in oncogene activation or the aberrant expression of tumour suppressor genes. In the recent past, case reports and tumour registry studies on the risk of second cancer development have been important and have alerted the clinician that careful surveillance in this group of patients is required. More prospective hospital based studies are required to delineate the true risk of second malignancies in association with prostate cancer.