This study reviewed the immunophenotyping results of children with acute leukemia in Kelantan, Malaysia. In the 3.5-year period (January 1994 to June 1997), 45 cases were identified. All children were under the age of 12 years and the predominant ethnic group was Malay. Thirty-six cases (80%) were acute lymphoblastic leukemia (ALL) and 9 cases (20%) were acute myeloblastic leukemia (AML). Of the ALL cases, 3% were of B-cell and 22% of T-cell origin, and 96% of the B-lineage ALL were CD10 positive. All the AML cases expressed CD33 and 78% were positive for CD13. The incidence of mixed-lineage leukemias was 13.8% for My+ ALL and 11.1% for Ly+ AML.