A single subject design was used with two children with severe head injuries to examine the effects of familiar and unfamiliar auditory and visual stimulation on levels of consciousness. The results indicated that the treatments used in this study did not significantly improve levels of consciousness. To determine whether or not the familiar stimuli was more effective than the unfamiliar, changes in vital signs, including heart and respiratory rates, were examined in response to the stimulation. The results indicated a tendency for one of the subjects to respond more to the familiar stimuli than the unfamiliar; however, the results were not statistically significant. The use of a single subject experimental design for examining the effectiveness of treatments with this population is discussed, as well as implications for therapeutic interventions.