Ninety-five patients who had megaloblastic anaemia, and who lived in a subtropical climate, were studied to elucidate the importance of puerperium, malabsorption, gastric dystrophy, diet and infection in the aetiology of the disease. All 5 factors were found to be common, and to occur in a variety of combinations, producing a wide spectrum of illness variously resembling nutritional megaloblastic anaemia, sprue, pernicious anaemia and many stages in between. It is concluded that megaloblastic anaemia in this population is a multifactorial disease, and a tentative scheme, relating the aetiological factors, is drawn up. Neither serum vitamin B(12) levels, nor folate estimation in serum or red cells emerged as very reliable guides to the underlying biochemical deficiency.