The prognostic value of a dynamic liver-function test, based on the hepatic conversion of lidocaine to monoethylglycinexylidide (MEGX), in predicting multiple organ failure (MOF) was prospectively investigated in 28 critically ill patients after multiple trauma. The MEGX test and conventional static liver tests (bilirubin, aspartate aminotransferase, glutamate dehydrogenase, and factor V) were performed on days 1, 3, 5, and 7 after trauma. Patients were classified by a modified MOF score into a group without (n = 18) and a group with the MOF syndrome (n = 10). One patient who developed MOF on the basis of a bacterial septicemia was excluded from the general evaluation. No significant differences were observed in the MEGX values of the two groups on day 1. All patients who subsequently developed MOF, however, displayed a sharp decrease in their MEGX values between days 1 and 3. Analysis of the data using receiver operating characteristic (ROC) curves revealed that the results of the MEGX test on day 3 provided the greatest discriminating power between patients with and without subsequent MOF. A cut-off MEGX value of 30 micrograms/L on day 3 was associated with a prognostic sensitivity of 89% and a prognostic specificity of 94%.