The primary protein component of human pulmonary surfactant is a 32,000-dalton glycoprotein called surfactant-associated protein A. This protein is important for normal lung function, and its expression is developmentally regulated. Using a mapping panel of somatic-cell hybrids, we have localized the coding sequence for pulmonary surfactant-associated protein A to chromosome 10. Additionally, this sequence identifies two separate MspI restriction-fragment-length polymorphisms. Since there is a relative lack of polymorphic markers for chromosome 10, this sequence may be useful in linkage analysis.