Bilateral primary germ cell tumors of the testicle are rare. The last comprehensive review of the literature (1955) revealed a 1.6% incidence. However, during the past twenty years, cases have been reported more often, raising the questions of increased frequency due to prolonged survival following surgery and/or roentgen therapy for unilateral tumors. A search of the medical journals during the past two decades fails to show any increased frequency of bilaterality (1.56%). All general combinations of cell types may occur and the tumors may appear simultaneously or sequentially. Successive seminomas are seen more often followed in frequency by concurrent seminomas. Although 50% of the second primaries were diagnosed within five years, 3% of the patients developed the second tumor after 20 years, stressing the need for extended follow-up. Factors affecting the diagnosis, management and prognosis of bilateral testicular tumors are discussed. Four additional cases of bilateral germ cell tumors are described.