Autosomal dominant and autosomal recessive forms of hypophosphatasia have been reported; generally the clinical picture runs true to form in families. In each of 2 kindreds, 2 sibs were clinically affected by hypophosphatasia to a markedly different extent. One set of sibs showed the lethal (perinatal) and infantile forms. The other showed the dental and adult forms. In both families there was consanguinity, albeit distant, and clinical expression in sibs supporting autosomal recessive inheritance.