The Papillon-Lefèvre syndrome (PLS) is segregating in a large kindred of a Jewish isolate originating from Cochin, India. The frequency of the gene responsible for PLS among the Cochin Jews, 0.1, was estimated from the number of unrelated carriers in the isolate who married into the kindred. The obvious discrepancy between this apparently high gene frequency and the total absence of PLS in other kindreds of the isolate suggests that the syndrome may not behave as a simple autosomal recessive trait.