Autopsy records of 600 profoundly retarded and 405 less retarded were examined for a thirty-one-year period at Pacific State Hospital. The profoundly retarded were found to have more respiratory infections at autopsy, and more deaths of such infections. Profound retardation was a particularly outstanding risk when in combination with epilepsy, inability to ambulate, and developmental cranial anomalies. Non-infectious respiratory morbidity and mortality are more common in the less retarded, apparently because of their living longer to develop these complications.