Hereditary elliptocytosis (HE) is a heterogeneous group of red-cell disorders. One class of HE patients was shown to have a mutated erythrocyte membrane skeletal protein 4.1 gene. We have recently shown that human protein 4.1 contains multiple isoforms with novel sizes, functions, and tissue-specific expression. Here, we report the subregional localization of this gene to human chromosome 1p33----p34.2, based on the fractional length, by nonradioactive in situ hybridization.