Acute lymphoblastic leukemia (ALL) in elderly patients (59 years or older) carries a poor prognosis, and this finding may be attributed to the relatively high frequency of the Philadelphia chromosome (Ph). To test this hypothesis, we reviewed the clinicopathologic features of 23 consecutive, newly diagnosed elderly patients with ALL (14 men, 9 women, aged 59-92 years) uniformly treated at our institution and compared the Ph+ and Ph- groups. Conventional cytogenetic data were available for 21 of 23 cases; 7 (33%) were Ph+. All Ph+ cases were of precursor B-cell type. The remaining 16 tumors were of precursor B-cell (10), mature B-cell (2), precursor T-cell (3), and mixed precursor T-cell/B-cell (1) type. Ph+ and Ph- groups did not differ significantly in median survival (13.4 months vs 19.0 months) or other variables studied. The Ph may not be a significant adverse prognostic factor in ALL in elderly patients.