The Laurence-Moon-Biedi syndrome is an ill-defined symptom complex usually presenting the signs of obesity, hypogenitalism, retinitis pigmentosa, polydactyly and mental deficiency. The case reported here is the first presented to a psychiatric hospital as a behavior disorder. In addition, this same patient, on the basis of behavior, physical appearance and laboratory determinations had been previously misdiagnosed as having Cushing's syndrome.The literature pertaining to the Laurence-Moon-Biedl syndrome is reviewed with particular reference to psychiatric and endocrinologic data. Closer psychologic scrutiny of this patient revealed that his mental deficiency may have been secondary to brain damage and not part of a genetically linked symptom complex. An appraisal of previous reports indicates a lack of effort at making this distinction in the past. The question of the usefulness and validity of viewing the symptom aggregate of Laurence-Moon-Biedl patients as a discrete, genetically transmitted syndrome is discussed.