We describe the clinical presentation, course, and treatment response of a 14-year-old boy with catatonic stupor. This patient, with a preexisting diagnosis of autism, displayed mutism, akinesia, and an extreme level of rigidity, waxy flexibility, posturing, including the psychological pillow, facial grimacing, and other involuntary movements of his upper extremities. In addition he had symptoms suggestive of a depressive disorder as well as some non-specific psychotic symptoms. Intravenous injection of sodium amytal failed to resolve any motor symptoms, although he showed a good response to the zolpidem test. A course of electroconvulsive therapy (ECT) caused dramatic and sustained relief of catatonic stupor without a change in the symptoms of autism. The presentation of catatonia in autism and the use of ECT in children are discussed, and the available literature reviewed. This is the first description of the use of ECT in the treatment of catatonia coinciding with autism and we confirm its efficacy.