Between 1979 and 1990, 149 patients with non-metastatic thymomas were treated in ten French cancer centers. Patients were staged according to the 'GETT' classification, derived from that of Masaoka. There were 13 stage I patients, 46 stage II, 58 stage III and 32 stage IVA. Gross total resections were performed in 63 cases, subtotal resections in 31 cases and in 55 cases a biopsy alone was performed. All patients received radiotherapy and 74 were given post-operative chemotherapy. Median follow-up was 7.7 years. Local control was achieved in 117 cases (78.5%) and was influenced by the stage of the disease (p < 0.01) and the extent of surgery (p < 0.01). Twenty-six patients developed metastatis after a median period of 9 months. Five- and ten-year disease-free survival rates were 59.5% (51-67%) and 49.5% (39-60%), respectively, and were influenced by the stage of the disease (p < 0.01), the extent of surgery (p < 0.001) and a mediastinal compression on presentation (p = 5 x 10(-6)). Four factors could predict a worse overall survival in the multivariate analysis: mediastinal compression on presentation (p < 0.001), absence of chemotherapy (p < 0.001), biopsy alone (p = 0.003), and young age (p = 0.013). A worse DFS was predicted by mediastinal compression on presentation (p < 0.001), absence of chemotherapy (p < 0.001), young age (p = 0.006), and stages III-IVA (p = 0.04). Future therapeutic strategies are discussed and the literature is reviewed.