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There are two accepted mechanisms to explain the origin of runaway OB-typestars: the Binary Supernova Scenario (BSS), and the Cluster Ejection Scenario(CES). In the former, a supernova explosion within a close binary ejects thesecondary star, while in the latter close multi-body interactions in a densecluster cause one or more of the stars to be ejected from the region at highvelocity. Both mechanisms have the potential to affect the surface compositionof the runaway star. TLUSTY non-LTE model atmosphere calculations have beenused to determine atmospheric parameters and carbon, nitrogen, magnesium andsilicon abundances for a sample of B-type runaways. These same analytical toolswere used by Hunter et al. (2009) for their analysis of 50 B-type open clusterGalactic stars (i.e. non-runaways). Effective temperatures were deduced usingthe silicon-ionization balance technique, surface gravities from Balmer lineprofiles and microturbulent velocities derived using the Si spectrum. Therunaways show no obvious abundance anomalies when compared with stars in theopen clusters. The runaways do show a spread in composition which almostcertainly reflects the Galactic abundance gradient and a range in thebirthplaces of the runaways in the Galactic disk. Since the observed Galacticabundance gradients of C, N, Mg and Si are of a similar magnitude, theabundance ratios (e.g., N/Mg) are, as obtained, essentially uniform across thesample.

The Origin of B-Type Runaway Stars: Non-LTE Abundances as a Diagnostic