Enteral nutrition can be administered as bolus feedings or by pump-assisted continuous drip. We have compared these two techniques in regard to bacterial contamination of nutritional solutions for given periods of administration set utilisation. A total of 103 patients were treated for 3 months. Bacterial contamination of nutritional solutions was important, but clinical complications, particularly diarrhea, were seen only in 11%. In several cases osmotic diarrhea was produced by too rapid administration. Factors associated with a high level of bacterial growth included utilisation time of administration sets, hanging time of feeding formula, and, mainly, maintenance of the connection between the administration set and the nasogastric tube during pump-assisted continuous drip. Retrograde colonisation of the nasogastric feeding tube is likely in view of the bacterial flora identified. The absence of relationship between microbial contamination of nutritional solutions and infectious diarrhea, as demonstrated in this study, is indicative of the appropriate bacterial safety of continuous drip or bolus enteral nutrition.