In April–May 1991 the availability of antibiotic formularies in Dutch hospitals was analysed as well as data available on antibiotic susceptibility patterns. In addition data on the use of different groups of antimicrobial agents (aminoglycosides, β-lactam compounds including aztreonam and imipenem, co-trimoxazole, vanco-mycin and fluoroquinolones) were collected by a questionnaire. Thirty-eight formularies were received which were used in 78 hospitals. No formulary was available from 31 hospitals: 15 hospitals did not intend to set up antibiotic guidelines, nine hospitals were using their first formulary and seven used a revised version of the existing one. Fifteen formularies dated from 1987 or earlier. The availability of antibiotic susceptibility patterns ranged from no data at all ( n = 14) to extensive data per species, per agent and per ward ( n = 5). From 20 hospitals data on antibiotic usage as well as on antibiotic guidelines were obtained. Because several hospitals used the same formulary, 15 different formularies were analysed from 20 hospitals. Fluoroquinolones were used in all hospitals, but were only mentioned in the formularies of six hospitals. The data in the present study underscore the need for a collaborative approach of medical staff, hospital pharmacy and microbiologist in order to maintain a relatively low level of antibiotic resistance in Dutch hospitals.