Summary. Background: Recombinant activated factor VIIa (rFVIIa) is used to treat bleeds in hemophilia patients with inhibitors. A subcutaneous formulation could potentially improve its half-life and make it suitable for prophylactic treatment. Objectives: A study was conducted to determine the safety of subcutaneously administered rFVIIa in patients with hemophilia and the pharmacokinetic profile (including bioavailability). Patients/Methods: This was a multicenter, open-label, cross-over comparison of single doses of intravenous rFVIIa 90 μg kg−1 and a new formulation of rFVIIa for subcutaneous injection at dose levels of 45, 90, 180, 270 and 360 μg kg−1. Sixty subjects (12 per dose cohort) with hemophilia A or B were enrolled. Results: Subcutaneously administered rFVIIa showed lower mean peak plasma concentrations and prolonged FVII activity (Cmax, 0.44–5.16 IU mL−1 [across doses]; t1/2, 12.4 h; tmax, 5.6 h) compared with intravenously administered rFVIIa (Cmax, 51.7 IU mL−1; t1/2, 2.7 h; tmax, < 10 min). The absolute bioavailability of subcutaneous rFVIIa ranged from 21.1 to 30.1% across dose levels. Dose proportionality was observed within a 2-fold dose increase but not across the full dose range. No thromboembolic events, drug-related serious adverse events, severe injection-site reactions or neutralizing antibodies were reported (primary endpoint). Mild and moderate injection-site reactions were more frequent with subcutaneous than with intravenous injections. Conclusion: This phase I clinical trial did not identify safety concerns of prolonged exposure to rFVIIa administered subcutaneously in single doses to hemophilia patients.