Six cases of congenital hemolytic jaundice with "hemolytic" crises are reported. It is demonstrated that during the development of the anemia an acute aplastic condition is present in the erythropoietic tissue of the bone marrow with complete cessation of the formation of red cells. The reticulocytes disappear from the blood; jaundice, serum bilirubin and urobilinuria decrease to normal values; and the serum iron increases. This period is further characterized by leukopenia and thrombocytopenia. The spontaneous recovery is caused by a rapid regeneration of the erythropoietic tissue resulting in a marked reticulocytosis in the peripheral blood, and there is also leukocytosis, an increase in thrombocytes and a rapid fall of serum iron. During the period of severe anemia an increase in the blood urea and uric acid occurs. Transfusion experiments revealed an average lifetime of approximately fifteen days for the red cells in congenital hemolytic jaundice, a fact which fully explains the development and symptoms of the crisis as a result of cessation in the formation of red cells. The findings definitely contradict the theory that an acute increase in the hemolytic process is the reason for the crisis. The crisis should be called aplastic and not hemolytic.