This report describes the process of establishing a second WHO International Standard for Bleomycin complex A2/B2. Material was donated by a manufacturer and processed by EDQM. 8 laboratories participated in a study where they estimated potencies of the candidate material using microbiological assays. Statistical analysis of the results showed the candidate batch was homogeneous and stable. It is proposed that the second WHO International Standard for Bleomycin complex A2/B2 be assigned a potency of 12,500 IU/vial.