Irrational prescribing is a global phenomenon. The objective of this study was to find out the prescribing practices of antimicrobials in a general hospital in Damanhour by evaluation of the extent, pattern and factors influencing use. A retrospective study was conducted from January 2000 through December 2000. A total of 732 medical records were selected by systematic random sample from inpatient medical records of all departments of the hospital. Prescribing pattern was analyzed using WHO basic drug indicators. The average number of antimicrobials during hospital stay was 1.7 and 80.6 % of all prescriptions contained at least one antimicrobial. About one fourth [23.8 %] of prescriptions entailed repetition of the same antimicrobial group. The most frequently used antimicrobial groups were cephalosporins [42.7 %] followed by penicillins [23.6%] and aminoglycosides [13.2 %]. The majority [88.64 %] of antimicrobials used were bactericidal. The average cost / patient for all antimicrobials during hospital stay was 82.78 L.E. Almost 70 % of antimicrobials were prescribed as injections. Prophylactic use of antimicrobial was found in about two- thirds [67.8 %] of prescriptions. In the majority of cases [96.4 %] antimicrobials were given without bacteriological proof. After controlling confounding, the most important predictors of antimicrobials use were operative interference, longer duration of hospital stay [> 1 week], younger age of the patient [less than 1 year] and paid treatment. Rational antimicrobial policy, Infection Control Committees and educational programs for prescribers on rational use of antimicrobial are recommended.