A two-compartment minimal model (2CMM) has been proposed [A. Caumo and C. Cobelli. Am. J. Physiol. 264 (Endocrinol. Metab. 27): E829-E841, 1993] to describe intravenous glucose tolerance test (IVGTT) labeled (hereafter hot) glucose kinetics. This model, at variance with the one-compartment minimal model (1CMM), allows the estimation of a plausible profile of glucose production. The aim of this study is to show that the 2CMM also allows the assessment of insulin sensitivity (SI2*), glucose effectiveness (SG2*), and plasma clearance rate (PCR). The 2CMM was identified on stable-isotope IVGTTs performed in normal subjects (n = 14). Results were (means +/- SE) SG2* = 0.85 +/- 0.14 ml.kg-1.min-1, PCR = 2.02 +/- 0.14 ml.kg-1.min-1, and SI2* = 13.83 +/- 2.54 x 10(-2) ml.kg-1.min-1.microU-1.ml. The 1CMM was also identified; glucose effectiveness and insulin sensitivity indexes were SG*V = 1.36 +/- 0.08 ml.kg-1.min-1 and SI*V = 12.98 +/- 2.21 x 10(-2) ml.kg-1.min-1.microU-1.ml, respectively, where V is the 1CMM glucose distribution volume. SG*V was lower than PCR and higher than SG2* and did not correlate with either [r = 0.45 (NS) and r = 0.50 (NS), respectively], whereas SI*V was not different from and was correlated with SI2* (r = 0.95; P < 0.001). SG* compares well (r = 0.78; P < 0.001) with PCR normalized by the 2CMM total glucose distribution volume. In conclusion, the 2CMM is a powerful tool to assess glucose metabolism in vivo.