Data on all patients diagnosed with Philadelphia chromosome-positive (Ph+) acute lymphoblastic leukemia (ALL) aged 55 or older, seen in our institution over a 17-year period, were studied to determine the incidence and range of clinical and biological subtypes, and the outcome of different therapeutic approaches. Twenty-five Ph+ ALL cases (median age: 64 years) were diagnosed between 1986 and 2003 (28% of all B-lineage elderly ALL seen during this period). Karyotypic analysis was performed successfully in 22 cases, while 3 were only diagnosed by molecular biology analysis. All patients had B-cell lineage ALL. Co-expression of myeloid markers was observed in 20% of tested cases. One patient died before chemotherapy could be given. All other patients received "curative" treatment according to different protocols used during the period of study. Overall the complete remission (CR) rate was 76% (95% confidence interval, CI: 55-91%). Fifteen patients achieved CR after one course of chemotherapy and 4 patients after salvage therapy. Median disease-free survival (DFS) of the entire cohort was 5.6 months (95% CI: 4.5-8.4 months) and median overall survival was 10.1 months (95% CI: 7.9-13 months). In multivariate analysis, age>or=70 years was of poor prognostic value for achieving CR (p=0.05) and hyperleukocytosis at diagnosis was of poor prognostic value for overall survival (p=0.001). Overall survival duration was not significantly influenced by achieving CR. Ph+ ALL patients did not show a significant difference in terms of outcome as compared with Philadelphia-negative ALL patients. The very poor overall outcome in elderly patients with Ph+ ALL may be significantly improved by the introduction of imatinib mesylate into current treatment regimens.