The use of humor in psychiatric care and treatment is examined within a life-span-development context, comparing its utility in late adolescence with that in early adulthood. The literature of the past two decades, based on careful experimental research as well as on more subjective clinical experience, tend to support the following conclusions: A well-developed sense of humor provides a beneficial ingredient to the patient's coping or adjustive ability. The salutary physiological effects of laughter are the same for adolescents and adults. In terms of psychosocial factors, individual rather than developmental stage differences in the patient's personality, psychopathology and humor preference will alter the effectiveness of humor application. According to a cognitive-behavioral analysis, the mechanism by which positive emotions (including laughter) operate to reduce or eliminate the undesirable negative emotions resides in the interplay of the physiological and psychological processes involved in the stress reaction and its management. Finally, to be optimally effective the psychiatrist should undertake formal training in the use of humor techniques comparable to the traditional training in the usual assessment and therapeutic procedures.