The frequent use of antibiotics, and the ensuing increase in bacterial resistance, has caused much concern in the medical community in recent years. This study examines antibiotic prescribing from various perspectives, utilising prescribing information from several sources including market research databases, a provincial prescription drug plan, hospital records and patient-specific information obtained through chart review. Overall quantities and types of antibiotics prescribed have been studied at a national level comparing both Canada and the USA. at a provincial level using prescription claims data for specific facets of the Newfoundland population, at the community practice level utilising chart review of a representative sample of patients in the communities of St. John's and Mount Pearl, Newfoundland and at the hospital level using chart review. -- Examination of national prescribing databases and the Newfoundland provincial database has demonstrated similar prescribing trends. Amoxicillin was the most commonly used antibiotic, penicillins accounted for the greatest proportion of total antibiotic prescriptions, a decrease in the amount of penicillins used was noted, and an increase in macrolide use was seen across all three longitudinal databases. The cross- sectional study of community practices in St. John's demonstrated that amoxicillin was the most frequently used antibiotic, and the proportions of total antibiotic use comprised by each antibiotic drug class were similar to those seen in Canada. -- The Ontario Anti-infective Guidelines for Community-acquired Infections' was chosen as the tool for measuring prescription appropriateness in community practice. When the physicians' diagnoses were assumed to be correct, 59% of prescriptions were appropriate. Using a criteria-based decision tree to predict etiology, 88% of respiratory tract infections were likely to be viral, while the physicians thought that only 44% were viral. The treatment recommendations outlined by the Canadian Community Acquired Pneumonia Consensus Conference Group2 were used to assess appropriateness of antibiotic treatment in patients admitted to hospital with community acquired pneumonia. Sixty five percent of initial antibiotics and 59% of secondary oral antibiotics were appropriate. However prescribing guideline adherence was much lower for patients with less severe community-acquired pneumonia. -- To decrease inappropriate and excessive antibiotic use, it is necessary to first determine the nature of antibiotic prescribing. The results from this analysis allow for specific problematic areas in antibiotic prescribing to be identified. From this, interventions to improve prescribing behaviours can be implemented.