Stressors faced by UCEs concern lack of management commitment, personal problems, personal relationships with suspects, overidentification with suspects and loss of personal identity, fear of discovery, technical difficulties, interagency cooperation, lack of recovery time, lack of context, and unsuitable roles. Those most suited for undercover work have the resilience to overcome undercover stressors and pitfalls and to build relationships. Police supervisors should conduct adequate research to identify UCE needs and to develop certified UCEs who have the necessary psychological attributes to meet the challenges of undercover work. Desirable attributes of UCEs are identified, and the appropriate amount of time UCEs should spend in undercover work and the reintegration of UCEs back into regular police work are discussed. 2 endnotes and 2 photographs