Although humor is a key element of all social interactions and is frequently present in the psychotherapy process, rarely do therapists consciously and purposely use humor with therapeutic intent. Each theoretical orientation helps clients change emotions, behaviors, and/or cognitions. Humorous interventions can activate change in each of these central areas of human experience.A key unanswered question is how therapeutic humor is generated. This question has been virtually ignored. Unless people specify the elements that facilitate the creation of therapeutic humor, they cannot train practitioners to be therapeutic in their use of humor. Using Carl Rogers' (1957) "necessary and sufficient conditions" as a central theme, this article addresses the nature of the practitioner that is necessary for therapeutic humor to be communicated to the client. It further describes the qualities of the client/ receiver of the humor that are necessary for therapeutic humor to be experienced, and, finally, it specifies the nature of the interactive relationship that influences the potential for humor to be therapeutic. It is the interaction of the skills and qualities of the therapist, the qualities of the client, and the nature of the bond of the relationship between them that accounts for the client's experience of therapeutic humor.