['Insulin resistance is intrinsically related to intramyocellular (IMCL) rather than extramyocellular (EMCL) triglyceride content. Conflicting results have been reported on the ability of insulin sensitizer agents, such as thiazolidinediones, to modify muscle fat distribution. The aim of this study was to investigate the role of rosiglitazone on muscle fat compartment distribution in an adult population of obese non-diabetic metabolic syndrome patients.', 'Fifteen obese, non-diabetic, metabolic syndrome patients were studied by means of proton nuclear magnetic resonance ((1)H-NMR) spectroscopy before and after treatment with rosiglitazone 8 mg/day for 6 months. Anthropometrical and metabolic variables were assessed.', 'After rosiglitazone, body weight and hip circumference increased [100.9 (91.12-138.7) vs. 107.0 (79.6-142.8) kg and 118 (107-126) vs. 122 (110-131) cm]; while waist-hip ratio (WHR) decreased from 0.93 (0.87-1.00) to 0.89 (0.82-0.97) (P < 0.001 for all). Additionally, fasting plasma glucose, insulin and homeostatis model assessment of insulin resistance (HOMA-IR) significantly decreased while adiponectin increased over threefold [9.7 (3.7-17.7) vs. 38.0 (19.3-42.4) microg/ml] without any changes in resistin. Finally, the IMCL did not change [267.54 (213.94-297.94) vs. 305.75 (230.80-424.75) arbitrary units (AU), P = 0.15] while the EMCL increased [275.53 (210.39-436.66) vs. 411.39 (279.92-556.59) AU; P < 0.01] therefore decreasing the IMCL-to-EMCL (IMCL/EMCL) ratio [1.07 (0.78-1.23) vs. 0.71 (0.53-0.96); P < 0.01].'] Does rosiglitazone decrease intra- to extramyocellular fat ratio in obese non-diabetic adults with metabolic syndrome?