Pseudoachondroplasia (PSACH) is a wellcharacterized autosomal dominant dwarfing condition. A great deal of information is available about orthopedic complications, but little is known about extraskeletal complications in adulthood. This study was undertaken to delineate the natural history of PSACH at all ages. Seventy-nine individuals responded to an extensive questionnaire that included information about deformities, operations, general health, chronic diseases, and reproduction. PSACH individuals were ascertained through the University of Texas Medical Genetics patient population, a genetic linkage study, and the social organization, Little People of America. The results show that PSACH individuals with a family history do not have a distinct or more severe phenotype than new mutation cases. There were no differences in the number of orthopedic complications, operations, or number of offspring between these two groups. Less than half of affected adults reported having total hip replacement surgery, which was less common than previously reported. Extraskeletal complications were generally uncommon. There were four cases of cancers in 4 1 individuals queried. Premature osteoarthritis was the major health problem for PSACH individuals. PSACH individuals are generally healthy but have problems associated with debilitating osteoarthritis.