The putative oncogene pim-1 is frequently activated by provirus insertion in MuLV-induced T cell lymphomas in mice. By analogy with other cellular oncogenes that are similarly activated (e.g., myc, myb, erbB) it is possible that pim-1 may also be involved in some human tumors. To study human pim-1 we cloned and sequenced human pim-1 cDNA clones. The human pim-1 codes for a protein of 313 amino acids (aa) which is highly homologous (94%) to the deduced amino acid sequence of mouse pim-1. All the mouse pim-1 residues which are homologous to protein kinases are conserved in the human pim-1. We also isolated the human pim-1 gene and mapped it relative to the cDNA. The RNA transcript of human pim-1 is approx. 3.0 kb and it is highly expressed in the erythroleukemia cell line K562.