Research has indicated that HIV service providers commonly use humor to cope with work-related stress; however, little is known about the forms and functions of humor used by these professionals. In this study, 25 HIV service providers from five AIDS service organizations were interviewed about their use of humor. Participants described five primary types of humor as prevalent within AIDS service organizations and noted that humor served a variety of functions, which were either adaptive or maladaptive. Adaptive functions included boosting morale and reducing tension, whereas maladaptive functions ranged from masking emotions to alienating certain groups. Results emphasized the importance of context in the study of humor use and the need for continued investigations of the stress and coping of HIV service providers.