A prospective decision-aiding trial was performed to select drugs for regional chemotherapy of various liver tumors (n = 36) by individual drug testing. The drugs were chosen for hepatic artery infusion according to the individual chemosensitivity of tumor biopsies in the human tumor colony-forming assay (HTCA). In vitro HTCA sensitivity correlated with complete response (CR) + partial response (PR) + no change (NC) 93% of the time and with CR + PR 55% of the time. The test sensitivity was 90%, and the specificity was 67% for CR + PR + NC versus progressive disease (PD), whereas the sensitivity and specificity were 89% and 28%, respectively, for CR + PR versus NC + PD. The overall predictive accuracy of the test was 86% for CR + PR + NC versus PD and 58% for CR + PR versus NC + PD. Overall, 83% of this heterogenous patient group with various tumors achieved CR + PR + NC and a 50% clinical response (CR + PR). In vitro-sensitive patients showed a significantly lower intrahepatic progression rate (7% PD) than in vitro-resistant patients (57%; P < 0.05). These results indicate that the HTCA could identify active drugs for individualized hepatic artery infusion, and patients may profit from the use of in vitro-sensitive drugs.