Immature teratomas with peritoneal gliomatosis are rare. Eight cases have been registered by the Dutch Ovarian Tumor Committee and one patient, presented in this paper, was treated recently. The follow-up in these cases indicates a good prognosis, even in grade 2 teratomas. Peritoneal implants do not influence adversely the prognosis when they are composed of mature glial tissue. A conservative approach seems to be justified.