Primary open-angle glaucoma is a major cause of irreversible blindness in Western countries for which there is presently no curative treatment. Linkage of hereditary juvenile glaucoma with chromosome 1q21-q23 was recently described in 2 American families. Here we have studied two large French pedigrees with a similar form of familial autosomal dominant juvenile-onset glaucoma. Linkage of glaucoma with chromosome 1 was confirmed in these 2 families. Maximal lod-score of 7.60 was reached at the D1S212 marker for a recombination fraction of 4.4%. The typing of this marker should facilitate the screening of glaucoma families and the identification of individuals at risk for the disease. It will also provide a reference to evaluate the genetic heterogeneity of glaucoma.