OBJECTIVES: To understand how different evidence bases may contribute to health technology assessment (HTA) across jurisdictions, we reviewed the evidence considered by three HTA agencies supporting reimbursement recommendations for nine drugs. METHODS: We selected nine drugs for which the Canadian Common Drug Review (CDR), the Australian Pharmaceutical Benefits Advisory Committee (PBAC), and the National Institute for Health and Clinical Excellence (NICE) had each provided recent reimbursement recommendations. We reviewed the clinical and economic evidence considered for each decision and evaluated whether different evidence bases could have contributed to different HTA decisions. RESULTS: The three HTA agencies agreed (recommended to reimburse) for four drugs and reached different recommendations for five drugs. In both categories, somewhat different evidence bases were used by each agency. For a given drug, different comparators were sometimes considered by different agencies. Even when comparators were common across agencies, there was variability regarding which clinical trials were considered. All agencies considered data from direct, randomized trials, but PBAC and NICE accepted indirect comparisons, whereas CDR did not. Regarding economic outcomes, all NICE decisions made use of cost-effectiveness (mostly cost-utility) analyses, but cost-minimization approaches were considered by CDR and PBAC for several drugs.  Overall, NICE provided the most transparent reporting on decision making, and CDR was generally the least transparent of the three. CONCLUSIONS: HTA drug decisions across the three countries lack good agreement, and considerable variability exists in the clinical and economic bases considered by CDR, PBAC, and NICE. The reluctance of CDR to accept indirect clinical comparisons, and the propensity of NICE to heed expert advice when analyses were inconclusive may contribute to dissimilar decisions being reached for some drugs. Greater transparency and harmonization of HTA methods have the potential to improve efficiency in health care decision-making, and further research analyzing additional HTA drug decisions is warranted.