In previous studies of up to 2 years' duration, mycophenolic acid has been shown to be an effective psoriasis suppressant. As the result of questions raised regarding the possible immunosuppressive and carcinogenic potentials of the drug, in addition to its apparent acute gastrointestinal side effects, widespread clinical trials were discontinued in 1977. We were given the unique opportunity of continuing to administer the drug on a compassionate-use basis to 85 patients for up to 13 years. In this review we report continued efficacy without dose escalation. Gastrointestinal side effects, prominent in the early years of the study, became infrequent. Although 11.6% of the patients developed uncomplicated zoster, no clinical evidence of immunosuppression was noted. The seven malignant neoplasms that arose in six of the patients were not unusual considering the age of the study population. Six patients died of conditions believed to be unrelated to drug therapy. We continue to believe that mycophenolic acid is an effective drug for the treatment of moderate to severe psoriasis and that the risks of its long-term administration are acceptable. With appropriate clinical and laboratory monitoring it can be given safely to patients who cannot take methotrexate and who may not be candidates for PUVA, retinoids, or other systemic chemotherapy.