This report describes the hereditary occurrence of severe laryngomalacia in three of five siblings of a Mexican-American family. The mother, who experienced respiratory difficulties in the first year of life, may also have been affected. All three affected children required neonatal tracheostomy, and two died of pulmonary complications. Histological studies of tracheal cartilage revealed distinct hypercellularity and histochemical staining abnormalities of the cartilaginous matrix without defects in skeletal cartilage. Although laryngomalacia is not uncommon, this disorder previously has not been documented to occur as a familial trait, nor have distinct abnormalities of cartilage been associated with laryngomalacia. This report suggests that etiologic and pathophysiologic heterogeniety exists for the clinical syndrome of laryngomalacia.