We investigated the influence of various clinical prognostic factors in patients with glioblastoma multiforme (GBM) treated with a combined modality approach. A total of 175 patients with GBM was treated in four consecutive prospective phase II studies using surgery, hyperfractionated or accelerated hyperfractionated radiotherapy (RT) and either adjuvant or concurrent or pre-irradiation chemotherapy (CHT) between January 1988 and December 1993. The median survival time for all 175 patients was 14 months and 1-3-year survival (OS) rates were 57%, 34% and 24%, respectively. The median time to tumour progression was 12 months, and 1-3-year progression-free survival (PFS) rates were 43%, 11% and 7%, respectively. Survival analysis showed that of all investigated prognostic factors, only gender did not influence survival. Patients </=55 years did better than those >55 years; patients with KPS 80-100 did better than those with KPS 50-70; patients with frontal tumours did better than those with tumours in other locations; patients with tumours up to 4 cm did better than those with larger tumours, as did patients with either subtotal or gross total tumour resection when compared to those undergoing biopsy only. Multivariate analysis showed that gender and tumour location did not independently influence survival. When PFS was used as the endpoint, only gender did not influence PFS, as confirmed by multivariate analysis.