The occurrence of calcareous renal stones in 12 members of a family was consistent with an autosomal dominant mode of inheritance. All 6 members with stones who were evaluated were shown to have absorptive hypercalciuria. The mother of 2 members with stones did not suffer stones but had biochemical evidence of absorptive hypercalciuria (increased intestinal calcium absorption, hypercalciuria and normal parathyroid function). Nephrolithiasis was encountered only in the progeny of members who had stones of biochemical absorptive hypercalciuria. The results suggest that physiological feature(s) of absorptive hypercalciuria may be an expression of the genetic trait.