Biochemical assays have demonstrated the existence of hormone receptors in lung tissue from patients with pulmonary lymphangiomyomatosis (LAM). This finding is the biologic corollary to the finding that LAM responds to hormonal therapy. We have examined lung tissue from two patients with LAM for estrogen and progesterone receptors by immunohistochemistry and a biochemical assay. Although specimens from both patients were negative for estrogen receptor activity by the biochemical assay, positive stain of estrogen receptors was observed in both patients with immunohistochemistry.