To gain a better understanding of the scope of previous research on psychiatric emergency services (PES) and to identify areas of focus for future studies, the author reviews PES literature published between 1983 and 2003. PES literature was identified by performing a MEDLINE search. The author was interested in studies or reviews of all types of PES. The refereed research, consisting of 85 articles, is a representation of the existing literature as multiple studies were found to be similar in topic and methodology. This review is organized using Donabedian's structure, process, outcome framework to describe research that has examined 1) providers, clients, and services; 2) variations in access, utilization, evaluation, treatment, and continuity of care; and 3) outcomes of these services. The resulting report reveals methodological limitations that are pervasive throughout the PES literature, dimensions of psychiatric emergency services that remain unexplored, and a PES research agenda.