For the presented study a computer-based surveillance system for detecting nosocomial infections (NI) with direct data input from attending on-ward physicians was implemented. During a 12-month period surveillance of ventilator-associated pneumonia (VAP) and catheter-associated bloodstream infections (BSI) was performed prospectively by on-ward physicians guided by infection control specialists on an 11-bed medical intensive care unit in a German university hospital. In 603 patients 3282 patient days were assessed. Completeness of data entry during the routine phase was 94% for ventilator days and 88% for central venous catheter days. The concordance of infection detection by automated evaluation and evaluation based clinical considerations was fairly good and was quantified by kappa measures of 0.49 for VAP and 0.57 for BSI. Detected infection rates ranged within the German national reference data. Personnel costs for on-ward physicians and infection control personnel were 1.01 Euro per device day in the routine phase. Time expenditure of less than 3 min per device day, rendered in about equal parts by physicians and infection control personnel, was lower than in studies relying on on-ward assessment by infection control personnel.