Rotational coherence spectroscopy (RCS), a time-domain approach to high-resolution rotational spectroscopy, is becoming increasingly important as a means of obtaining structural information on large species in the gas phase. In this article we consider the fundamentals of RCS and why the approach is useful in studies of large species. We also outline the various ways to implement RCS. Finally, we review structural results from this laboratory obtained from RCS experiments on aromatic-aromatic dimers, hydrogen-bonded complexes and clusters, aromatic-(rare gas), clusters, and large molecules with conformational degrees of freedom.