To determine if Tax regulated KDR expression, we examined mRNA and protein levels of KDR in Tax+ cells (C8166, MT-2, HUT-102, and SLB-1), uninfected control leukemic cell lines (Jurkat and HL-60), and Tax- ATLL cell lines (MT-1, ATL-2S, and TL-OM1). The gene discussed is KDR; the disease is adult T-cell leukemia/lymphoma.