As the biological behaviour of germinoma with syncytiotrophoblastic giant cells (STGC) is not well established, the present study was undertaken to ascertain the prognostic significance of serum hCG level in affected patients. Of a total of 23 cases studied, 12 patients were regarded as pure germinomas and 11 were germinomas with STGC. All but one of the former demonstrated an excellent outcome. The exception developed subarachnoid metastases, but the tumour disappeared on radiation therapy and the patient is enjoying a normal social life 13 years after the initial treatment. With the germinoma complicated by STGC, 3 cases showed local recurrence which were followed by a poor outcome. Their pretreatment hCG levels were 15.0, 26.0 and 29.6 mIU/ml respectively. The study showed a tendency, in germinomas with STGC, for a positive association between serum hCG, and the likelihood of a poor outcome. Germinomas with STGC and serum hCG levels higher than 15 mIU/ml thus have a high recurrence rate, and more aggressive treatment is indicated for the affected patients.