Title:Enhanced Nitrogen in OB-type runaways: a test for the Binary Supernova hypothesis Abstract: Two mechanisms have been accepted to explain the origin of runaway OB-type stars. In the Cluster Ejection Scenario (CES), close multi-body interactions in a dense cluster environment cause one or more stars to be ejected from the cluster at high velocity. In the Binary Supernova Scenario (BSS), a supernova explosion within a close binary ejects the secondary star due to the conservation of momentum. In this case CNO processed material should have been transferred to the secondary from the primary before the supernova explosion, leading to an enhanced N abundance in the runaway. High-resolution spectra from a sample of OB type runaways can be used to accurately determine N abundances. If N is found to be strongly enhanced, it will provide compelling evidence for the BSS mechanism, allowing us to assess the relative importance of the BSS and CES mechanisms.