This literature review on professional crime defines professional theft as the illegal taking by a professional criminal of another's property without the victim's knowledge or consent. Many variations in semantics, approach, methodologies, and conceptualizations create an array of conclusions from the studies reviewed. Few researchers dispute that there are career criminals similar to professional criminals. Two solutions address the question of how to define the career criminal versus the professional criminal. First, a revised version of Sutherland's behavior system approach would provide more homogeneous types, more consistent criminal samples, and more uniform results. Second, an ongoing series of phenomenological studies of professional criminals who have avoided frequent convictions would produce additional information. A total of 34 references are supplied.