Rationale: The 62005 EORTC phase III trial, comparing two doses of imatinib in patients with advanced GIST, reported a median progression-free survival of 25 months with a trend towards dose dependency for progression-free survival. The current analysis of that study aimed to assess whether histological/immunohistochemical parameters correlate with clinical response to imatinib. Patients and methods: Pre-treatment samples of GISTs from 546 patients enroled in phase III study were analysed for immunohistochemical characteristics, correlations with clinicopathological data, with survival and with tumours' genotype. Results: There was no correlation between immunomorphological or clinical characteristics and response to treatment, PFS or OS. No correlations between immunophenotype of the tumour and PFS or OS in the two dose arms were observed. Conclusions: The results confirm the heterogeneity of GIST in terms of immunophenotypic expression, but indicate that these parameters have no impact on the outcome of the patients under imatinib treatment. (C) 2008 Elsevier Ltd. All rights reserved.