We performed an observational study of the antibiotic-prescribing behaviour of Sicilian general practitioners (GPs) in managing acute upper respiratory tract infections (URTIs). Seventy-six GPs from 25 towns, representing a patient population of 96,630, participated in the study between September 1995 and May 1996. These physicians issued 2038 antibiotic treatment courses for acute upper respiratory tract infections: 792 for acute pharyngitis, 531 for acute tonsillitis, 304 for acute laryngitis and tracheitis, 268 for suppurative and non-suppurative acute otitis media, 124 for acute sinusitis and 19 for acute rhinitis. Forty-nine different antibiotics were prescribed. The most commonly used therapeutic groups were macrolides (38.6%), cephalosporins (27.1%), a combination of penicillins with beta-lactamase inhibitors (15.7%) and extended spectrum penicillins (13.5%). For each of the above diseases, except rhinitis, more than 30 different antibiotics were used. The choice of the route of administration appeared to be influenced by the age of the patients and, significantly, by a subjective clinical assessment of disease severity rather than by any consideration of epidemiological information or evidence from clinical trials. The rather marked variation in antibiotic-prescribing pattern for URTIs among Sicilian GPs reflects lack of availability or knowledge of any local or national guidelines.