J type diabetes is grouped as a subtype of type III or malnutrition-related diabetes, known as protein-deficient pancreatic diabetes, (PDPD). J type diabetes has not been reported recently, but a clinical picture called phasic insulin-dependent diabetes mellitus (PIDDM) has been elaborated in Jamaica, the same home country of PDRD and appears to be a "formes frustes" syndrome. The following comparative studies were performed on a group of diabetic patients and normal controls: insulin receptor binding; renal, hepatic, and pancreatic function; and abdominal ultrasonography. The results show a considerably decreased white and red blood cell binding to insulin (P less than .05), extensive kidney damage (P less than .05), and increased pancreatic echogenicity in PIDDM, supporting a separate identity of this latter syndrome from types I and II diabetes mellitus. Also, the features of relative insulin resistance, absence of ketosis even in the presence of severe hyperglycemia, and intermittent insulin requirement suggests that PIDDM, J type diabetes, and PDPD are one and the same syndrome.