BACKGROUND: It is believed that gonadal and extragonadal germ cell tumors (GCTs) arise from primordial germ cells and may have similar etiopathogenesis. Unlike testicular GCTs, there has been limited comprehensive population-based analysis of ovarian and extragonadal GCTs. METHODS: All malignant GCTs and all central nervous system (CNS) GCTs with benign and uncertain behavior that were registered in England in the age group 0 to 84 years from 1979 to 2003 were included in the current study. Incidence rates were calculated and adjusted to the world standard population. RESULTS: There were 33,364 GCTs (92.5% testes, 3.9% ovary, 3.2% extragonadal) in individuals aged 0 to 84 years. The CNS was the most common extragonadal site. An initial peak in incidence at ages 0 to 4 years of nongerminomas was observed at all sites except ovary. Second incidence peaks between ages 10 to 39 years that were more marked among males also were observed at all sites. The ages at these incidence peaks varied by site and were 10 to 14 years (CNS), 15 to 19 years (ovary), 25 to 29 years (other extragonadal sites), and 30 to 34 years (testes). A statistically significant increase in incidence over time was observed in germinomas (testes, CNS) and nongerminomas (testes, ovary). CONCLUSIONS: The age-incidence patterns observed suggested a common initiation of GCTs in embryonic/fetal life with variable rates of tumor progression as a result of subsequent events that may be site specific. The authors concluded that future genetic studies should consider GCTs from all sites to enable a better understanding of their etiology.