The fraction of field OB stars that originate from clusters can help probe the dynamical evolution of clusters. Field stars represent a significant fraction (20-30%) of the OB population in galaxies, and estimates for the fraction of field OB stars that are runaways range from the classical value of <10% (Blaauw 1961) to contemporary results suggesting >90% (de Wit et al. 2005). We obtained Magellan IMACS observations on the kinematics of field OB stars in the SMC to examine the line-of-sight velocities of this population. Using these observations, we will estimate the fraction of runaways to serve as a probe of cluster evolution.
