Investigations on the suitability of various alcohol fuels as alternatives to conventional diesel fuel were carried out on a passenger car swirl-chamber diesel engine. The test results with a methanol and an ethanol diesel fuel blend show that without alteration of the engine adjustment a good performance behaviour is obtained. In addition to a reduced soot emission and a considerably lower particulate emission the thermal efficiency mainly in the upper load range is higher than with pure diesel operation. The increased HC and CO emissions occuring at low loads can be avoided and a further improvement in energy consumption can be realized by adapting the injection timing for alcohol blend operation. A complete substitution of the diesel fuel with a methanol-ignition improver mixture necessitates an adapted and alcoho-resistent fuel injection system. A soot free combustion and with the exception of the NOX emissions nearly the same low level of gaseous pollutants as with pure diesel operation are achieved. In the full load range the thermal efficiency of the alcohol engine is distinctly higher, whereas at part load the efficiency turns out to be lower. With regard to the engine efficiency and the HC and CO emissions at low loads a further optimization of the fuel injection system is necessary.