Five families with DG6F deficiency were studied. Out of the first family, neinatal hyperbilirubinemia was evident in 3 children. Exchange transfusion was given to the first two. Possibly, the hemolytic crisis was subsequent to the application of vitamin K. In the next family group, there is a history of 6 children dead from jaundice and deep dark urine. Partial deficiency was found in the wife and 3 children from the third family. Fortunately, the father who is the brother of a deficient patient, shows normal levels. In family number four, both the father and the mother show below normal levels of DG6F. They have a sick son and daughter with subnormal levels. In the last family, the mother carried and the father shows abnormal levels of the enzyme; consequently, a son and their 2 daughters complain from the diseases. It is pointed out that some drugs, infections and several foods may precipitate the hemolytic crisis and brief comments are made on diagnostic and therapeutic resources.