BACKGROUND: Primary juvenile glaucoma is a rare form of glaucoma that typically affects individuals between 3 and 20 years of ages and is inherited as an autosomal dominant trait. One gene responsible for this condition has been localized to the 1q21-q31 region of chromosome 1. To investigate the clinical features of this form of glaucoma, the authors have examined the affected members of five pedigrees demonstrating genetic linkage to the 1q21-q31 locus. METHODS: Clinical characterization of 23 affected patients was performed. Genetic linkage to the 1q21-q31 locus was confirmed by segregation of the disease trait in each pedigree with genetic markers located in the 1q21-q31 region. RESULTS: The clinical features of affected members of the five pedigrees presented are generally homogeneous. The average age of diagnosis was 18.5 years (range, 5-30 years), and the average initial intraocular pressure was 38.5 mmHg (range, 30-53 mmHg). Eighty-seven percent of affected individuals were myopic and 83% of affected individuals required surgical treatment for glaucoma. There were no uniformly associated systemic or ocular conditions. One possible nonpenetrant carrier was identified and a difference in phenotypic expression of the presumed disease gene was observed in a pair of affected monozygotic twins. We also identified two pedigrees with juvenile glaucoma and three pedigrees affected by the pigment dispersion syndrome that are not genetically linked to the 1q21-q31 region. CONCLUSION: The form of juvenile glaucoma caused by a gene located in the q21-q31 region of chromosome 1 is generally phenotypically homogeneous. The severe elevation of intraocular pressure typically seen in affected patients suggests the product of the predisposing gene may participate in the outflow function of the eye.