The incidence of retroperitoneal tumours is extremely low (0.01-0.2% of all neoplasias). Their onset is atypical and a palpable mass is often clinically evident, together with abdominal pain and fever. A major impetus has been given to diagnosis by instrumental techniques, and in particular CT. Surgical treatment is required for these tumours. The prognosis does not improve following radio and chemotherapy. The authors describe 8 cases referred to their attention between 1980 and 1995.