We used automated laser fluorescence analysis of randomly amplified polymorphic DNA (RAPD-Alfa) to study the epidemiology of listeriosis in western Austria. There were no discrepancies between RAPD-Alfa patterns and serotypes found in 18 food isolates and 18 clinical isolates. The results of our study suggest that the food isolates typed were not at the origin of the human cases in western Austria. Using RAPD-Alfa, it was possible to link 9 out of 16 "sporadic" Listeria infections (mother-child cases counted as one) to the occurrence of other cases. Our results underline the necessity of epidemiological clarification of listeriosis cases as a prerequisite for specific preventive measures by public health services (e.g. confiscation of contaminated food products, issue of public warnings). To establish the chain of infection, more is needed than just speciation of bacteria in incriminated food products. Automated laser fluorescence analysis of randomly amplified polymorphic DNA seems a suitable, easy and rapid method for the typing of Listeria monocytogenes strains.