23 pages, via online journal., Organizational scholarship has rarely considered various hidden organizations in our society. Thus, little is known about how organizations and their members conceal their identity from others and how outsiders might evaluate the appropriateness of, effectiveness of, and motivations for organizational concealment. Our study reports survey data assessing 14 different hidden organizations and their perceived concealment efforts. Additionally, we examine the appropriateness of three motivations for concealment and three attitudes related to concealment. Results suggest similarities and differences in the effectiveness and appropriateness of concealment efforts by various organizations. Additionally, perceived motivations for concealment explain concealment efforts for some types of organizations, but not others. We draw several conclusions from our findings, discuss scholarly and practical implications of this research, and suggest directions for future scholarship related to organizational concealment.