Objective: We assessed whether alanine aminotransferase/aspartate aminotransferase (ALT/AST), a marker of hepatic steatosis, may be associated with adipose tissue dysfunction more closely than hepatic and muscle insulin resistance (IR). Methods: Associations with adipose tissue IR index (AT-IR) calculated as a product of fasting insulin and free fatty acids, leptin/adiponectin ratio, a proxy of adipocyte dysfunction, homeostasis model assessment IR (HOMA-IR), hepatic and muscle IR inferred from plasma insulin kinetics during a 75 grams oral glucose tolerance test (OGTT) were studied in nondiabetic 307 young and 148 middle-aged Japanese women, whose body mass index averaged 20 and 22 kilograms/m2, respectively. Results: On multivariate linear regression analysis in young women, ALT/AST was associated with trunk/leg fat ratio (standardized β = 0.202, P = 0.007), a marker of abdominal fat accumulation, and AT-IR (standardized β = 0.185, P = 0.003) independently of HOMA-IR and Matsuda index (R2 = 0.07). In middle-aged women, leptin/adiponectin ratio (standardized β = 0.446, P < 0.001) and AT-IR (standardized β = 0.292, P = 0.009) emerged as determinants of ALT/AST independently of trunk/leg fat ratio, OGTT-derived hepatic IR, leptin, and adiponectin (R2 = 0.34). Conclusions: ALT/AST was associated with AT-IR and adipocyte dysfunction more closely than hepatic and muscle IR even in nondiabetic lean Japanese women.