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Background: The aim of this study was to determine visceral fat accumulation and the fatty acid composition of serum phospholipids(PL) in middleaged female volunteers with different degrees of glucose tolerance and to analyze the factors that could be responsible for the observed differences between different degrees of glucose tolerance. Methods: Anthropometric measurements and computed tomography measurements at umbilicus and thigh midway between the patella and pubis were performed in 125 subjects with normal glucose tolerance(NGT), 62 subjects with impaired glucose tolerance(IGT) and 50 subjects with non-insulin- dependent diabetes mellitus(NIDDM), Normal weight subjects were divided into 3 groups; NGT, IGT and long term NIDDM and overweight subjects into 4 groups; NGT, IGT, newly-onset NIDDM and long- term NIDDM. An oral glucose tolerance test(OGTT), the fatty acid composition of serum PL, fasting serum levels of IGF-1 were determined. Results: Visceral fat area and visceral to subcutaneous fat ratio were higher in overweight control than normal weight control and higher in long-term NIDDM groups than controls. Thigh fat and muscle areas and serum levels of growth hormone and IGF-1 were lower in long-term NIDDM groups than controls. Insulin response area during OGTT was the highest in IGT groups and the lowest in NIDDM groups. The progression from the NGT group to the NGT and NlDDM groups was associated with an increase in glucose and free fatty acid areas during OGTT. Overweight long-term NIDDM group showed the lowest serum level of IGF-1 and the highest areas of glucose and FFA. The low ratio(about 0.64.~0.71) of polyunsaturated to saturated fatty acids in serum PL was found in diabetic groups. Long-term NIDDM groups showed an increase in proportions of palrnitic (C16:0), stearic(C18:0), dihomo-r-linolenic(C20:3w6) and docosapentaenoic(C22:3w6) and and a decrease in linoleic(C18:2w6), a-linolenic(C18;3w3), C20:4/20:3 (5-desaturase activity) and C18:1/18:0(9-desa- turase activity) in their serum PL compared with NGT groups. Conclusion: This study suggests that an increase in visceral fat and a decrease in thigh fat and muscle may be related to reduced secretion of growth hormone and insulin in long-term NIDDM subjects, These endocrine perturbations can be exacerbated by the prolonged exposure of hyperglycemia and high serum level of free fatty acid. In addition, lang term NIDDM may decrease 5-desaturase activity and 9-desaturase activity. Thus, the factors regulating fatty acid composition of serum PL in long-term NIDDM are affected by not only dietary fat but stored fat and serum concentrations of glucose and hormones, including insulin.