In 28 kitchens of restaurants and 10 kitchens of institutions, the hands of 280 persons were sampled in order to determine the role which hands play in contaminating food during preparation. The presence of salmonellae and the number of Enterobacteriaceae and Staphylococcus aureus in these samples was examined. No salmonellae could be isolated. However, large numbers (greater than 10(5)/hand) of Enterobacteriaceae and Staphylococcus aureus occurred on about 8% of the hands. "Normal" washing of the hands resulted in a lower number of transient micro-organisms. Since washing did not influence the number of Staphylococcus aureus on the hands, this organism seems to behave more as a resident organism. Prepared foods such as salads, fried meat and bread were often handled with relatively highly contaminated hands.