Purpose: The purpose of this review is to add to the discussion of assistant principals (APs), a position that has been under-represented in the professional literature. Design/methodology/approach: An extensive search was undertaken on assistant principals, vice principals, and deputy head teachers from various sources, including journals, conference papers, doctoral dissertations, ERIC documents, articles from professional publications and organizations, and relevant books and chapters. Each document was thoroughly analyzed and common themes were identified. Findings: The assistant principalship is a unique entity because the position lacks a precise job description yet entails numerous tasks to ensure the success of a school. Although the assistant principal is a critical leader in schools, the position is underutilized and under-researched. This review analyzes the roles, responsibilities, training, socialization, and typologies of the assistant principal. Research limitations/implications: As a result of this research, it is suggested that the role of the assistant principal needs to be reconfigured. Additional research is needed in the areas of training, professional development, and transition to the principalship. Originality/value: This article presents a unique comparison of the roles of APs throughout the past 30 years both in the USA and abroad. In addition, after examining the lack of university training and professional development for the assistant principalship, suggestions are made as to how APs can be better prepared for this critical leadership position. (Contains 1 table.)