Acholuric jaundice was not at first (1921) thought by the authors to be a mendelian dominant, since the disease seemed to be transmitted through 2 apparently healthy subjects. Data presented in this paper, however, indicate that apparently normal individuals may show the typical blood changes of acholuric jaundice (increased fragility of red cells, abnormal hemolysis, and a low percentage of hemoglobin) without other symptoms of the disease. When allowance is made for these, acholuric jaundice is inherited as a dominant mendelian character. The family described has 15 members with acholuric jaundice in 5 generations. Mendelian inheritance in some other diseases is also discussed: hereditary angio-neurotic edema, Milroy''s disease, fragilitas ossium and blue sclerotics, and polycystic disease of the kidneys.