We have compared the RNA expression of two oncogenes, H-ras and c-myc, with normal human lymphocytes, normal human T-cells, and human T-cell acute lymphoblastic leukemia (ALL). T-cell ALL RNA was derived from two human T-cell lines (MOLT-3 and CEM) and from five children with T-cell ALL. The RNA expression of H-ras and the third exon of c-myc was determined by northern hybridization. RNA from both MOLT-3 and CEM overexpressed both H-ras and the third exon of c-myc compared to normal lymphocytes and normal T-cells. T-cell ALL samples from four of five children overexpressed H-ras, while three of five patient samples overexpressed the third exon of c-myc when compared to normal lymphocytes and normal T-cells. Additional information on the oncogene expression of T-cell ALL may prove to be useful in the diagnosis and treatment of T-cell ALL.