The risk of suffering a second primary neoplasia after bearing a prostate cancer has been evaluated. The study patients attended the Hospital La Fe and were diagnosed between 1984 and 1992. There was a total of 223 prostate neoplasias, 22 of which had associated a second neoplasia and in 12 cases, corresponding to seven tumoral locations, prostate cancer was the first pathology to be diagnosed. Tumours observed were compared to those expected, according to the incidence rates appropriate for each age group and tumoral type, taken from the Spanish section of "Cancer Incidence in Five Continents", 1987. An excess of second neoplasias for vesical, kidney, CNS, bone and lymphoma tumours was found. In most cases, the second tumour was diagnosed between 6 to 12 months after diagnosis of prostate cancer. The patient's prognosis is dependent of the second neoplasia. The possible mechanisms of these associations are discussed in the light of state-of-the-art knowledge.