Murine serum inducible kinase (mSnk) was recently cloned and characterized as an early-growth response gene involved in cell proliferation. Here we report the isolation and characterization of its human homologue, named hSnk. Sequence comparison shows that hSnk is highly conserved and its deduced protein sequence shares a significant amino acid identity with mSnk and rSnk proteins, as well as with other polo family kinase gene products. A survey of hSnk expression reveals that while a wide variety of human tissues express a low to moderate level of hSnk transcripts, fetal tissues, testis, and spleen express the most abundant hSnk transcripts. In addition, serum stimulation rapidly induces hSnk expression in fibroblast cells, reaching the peak level of induction within one hour post treatment. Considering that Plk and Prk, two other known human polo-family kinases, control cell cycle checkpoint and cell cycle progression, our current observations suggest that hSnk may also play an important role in cells undergoing rapid cell division or having a high mitotic index.