During a 5-year period, data from all infectious disease (ID) consultations were recorded in a computerized database, which included 9068 new and 4937 additional consultations. The purpose of these 14,005 consultations was therapy (for 58%), diagnosis (for 13%), both (for 24%), and prophylaxis (for 4%); 51% were performed at the bedside, and the remainder were by discussion (19%) or telephone (30%). Recommendations included the following: initiation, change, or discontinuation of antibiotics (in 46%); performance of diagnostic tests (in 20%) or surgical procedures (in 1%); prophylaxis (in 3%); or no change (in 29%). Analysis of new versus additional consultations revealed significant differences. A new ID consultation was given at a rate of 6.0 consultations per 100 hospitalized patients; the rate per department correlated with the expenditure on antimicrobials per patient admission. During the study period, expenditure on antimicrobials per admission steadily decreased, from $44 in 1995 to $30 in 1999, a 35% reduction. In conclusion, analysis of data from ID consultations enables the ID service to evaluate its activity and to direct efforts to departments with high rates of nosocomial infections, antimicrobial resistance, and/or antimicrobial use.