OBJECTIVE To study the pattern of chromosomal abnormalities in adult patients with acute lymphoblastic leukemia. METHODS A retrospective study. METHODS January 1998 to June 2005 at the Cytogenetics department, Aga Khan University Hospital, Karachi. METHODS A retrospective analysis of cytogenetic studies was carried out in patients who were diagnosed as ALL and were more than 15 years of age. Cytogenetic analysis was performed using a trypsin-Giemsa banding technique. Karyotypes were interpreted using International System for Cytogenetics Nomenclature (1995) criteria. RESULTS The requests were received for cytogenetic analysis of bone marrow specimens in 69 patients who were diagnosed as ALL. Cytogenetic results were available in 62 patients; out of which 51 were males and 11 were females. 44 patients (70%) were found to have a normal karyotype. In 18 patients (29%), abnormal karyotype was found. CONCLUSIONS Cytogenetic studies should be part of the initial work up of every patient with ALL. Larger scale studies will help refine our understanding of the less common chromosomal patterns and conduct multivariate analysis to define the relative prognostic value of karyotypic results.