BACKGROUND: Microbial biological control agents (MBCA) are biopesticides based on living microbes. They have huge potential for the control of pests and diseases, but have trouble reaching the European Union (EU) market. According to several authors, this is caused by the regulatory regime, which is less supportive compared with that in the USA. The main objective of this paper is to present regulatory differences between the USA and the EU, and the resulting effects and developments of registration in both regions. RESULTS: Results show that EU registration is more complex due to differences between EU-and Member State (MS)-level processes, large actor heterogeneity and low flexibility. As a result, EU registration takes, on average, ∼ 1.6 years longer than US registration. Regulatory amendments have improved EU-level processes and led to a significant contraction of procedural time spans, but processes at the MS level have not improved and have become a larger procedural obstacle. CONCLUSION:The results correspond with the idea that EU registration is complex and lengthy compared with that in the USA. To improve regulation, national-level processes should be targeted for amendment. To that end, the authors suggest various ways of expanding the registration capacity of MS.