Mepolizumab proved efficacious for eosinophilic granulomatosis with polyangiitis (EGPA, former Churg-Strauss) at the dosage of 300mg/4 weeks in the randomized controlled MIRRA trial. Few successful real-life experiences with the dosage approved for severe eosinophilic asthma (100mg/4 weeks) were recently reported. We retrospectively assessed the effectiveness and safety of mepolizumab 100 and 300mg/4 weeks in a large European EGPA cohort.