Recently we isolated a cDNA clone corresponding to an epidermal serine proteinase inhibitor named SKALP (skin-derived antileukoproteinase). Here we report the chromosomal localization of the human gene encoding SKALP by Southern blot analysis of a panel of human x hamster hybrid cell lines and by nonradioactive in situ hybridization on R-banded human lymphocyte chromosome spreads. The SKALP-encoding gene has been assigned the approved symbol PI3 by the Human Gene Mapping nomenclature committee.