Abstract The growing number of biosimilars presents challenges to regulatory and health technology assessment (HTA) systems. This paper illustrates these challenges by focusing on biosimilars used in the oncological setting. In particular, discordances between data required by regulatory and HTA authorities potentially deprive patients of effective treatments and hinder optimal resource allocation. Regulatory and HTA authorities need to harmonize requirements to foster the development and widespread use of biosimilars, which potentially release considerable resources. The authors believe that often-inappropriate methodology creates a very real chance that HTA authorities will reject some biosimilars. This would effectively extend patent protection and, in the absence of competitor pressure from biosimilars, result in prices remaining unnecessarily high. The authors propose that HTA organizations should accept pharmacokinetic and pharmacodynamic equivalence between the brand and the biosimilar as a proxy of biological comparability. HTA organizations should then adopt, in the absence of compelling reasons otherwise, cost-minimization analysis (CMA) as the basis of the cost-effectiveness deliberations. In the absence of adequate studies demonstrating equivalent efficacy, a prerequisite of CMA, HTA organizations should require threshold analysis. Once approved, biosimilar manufacturers and regulators should maintain rigorous pharmacovigilance to exclude immunoreactivity or other rare adverse events. Furthermore, cancer centres and trusts should regularly audit and publish the impact of biosimilars on clinical outcomes and resource use. When appropriate, regulatory and HTA authorities should demand revised cost-effectiveness analyses from biosimilar manufacturers. This approach would hone the accuracy of the cost-effectiveness analyses, protect patients and allow health services rapid access to low cost treatments.