Portal pressures were estimated non-invasively in 100 patients who underwent hepatic resection and completely fulfilled the 21 variables evaluated. Ten variables were selected from among all those in the univariate analysis, and a stepwise discriminant analysis revealed four independent significant variables, namely: The indocyanine green dye retention test at 15 min (ICGR15); the prothrombin time index; the platelet count; and the globulin fraction. An equation to estimate the portal pressure was made using the coefficients in the analysis, the reliability of which was confirmed (r = 0.70484, P = 0.0001). The univariate analysis revealed ten significant variables to discriminate portal hypertension, defined as a portal pressure of over 200 mmH2O. A multiple logistic regression analysis of these variables revealed two independent variables, being ICGR15 and the platelet count. Thus, we consider that our equation for estimating portal pressure is potentially useful, and that the platelet count and ICGR15 are the most significant parameters in discriminating between the presence or absence of portal hypertension. Moreover, a platelet count of less than 120 x 10(3)/mm3 and an ICGR15 value of more than 15% correlated well with portal hypertension.