Pim-1 is a putative oncogene which was discovered as a target for transcriptionally activating proviral insertions in T-cell lymphomas in mice. Its genomic and cDNA sequence have been published (Selten et al., 1986, Cell 46, 603-611). We have isolated and sequenced pim-1 cDNA clones from the human leukemia cell line K562 (h-pim-1). Comparison of human and mouse cDNA sequences reveals that both contain: (i) a GC rich leader sequence, (ii) an open reading frame encoding a 313 amino acid protein (94% conserved) showing obvious homology to protein kinases and (iii) a 1.3 kb 3' untranslated region with two polyadenylation signals and five copies of the mRNA destabilizing motif ATTTA. "In vitro" translation experiments show that both mouse and human cDNA derived RNA can translate into a protein of the expected size. Their identity was confirmed by immuno-precipitation with antisera raised against synthetic pim-1 oligopeptides.