This paper reports on a meta-analysis of behavioural data gathered using single case research methodology, while evaluating the immediate effects of a treatment (sensory stimulation) on 24 individuals diagnosed as being in vegetative state following trauma. The data derived from time sampling have been used to compile measures of behavioural change in response to environmental events, which are referred to as arousal profiles. In addition to this, interviews were conducted regularly to elicit structured observations from the nursing staff concerning behavioural changes that they had observed. The subjects were divided into two groups according to whether they had emerged from vegetative state or not at the time the meta-analysis commenced. Statistically significant differences were found between the outcome groups in terms of modal arousal profile characteristics; one profile type was characteristic only of those that emerged. The two groups could also be differentiated by the mean recovery curves derived from the interviewdata. Behavioural differences between the outcome groups have been found which are detectable while the patients are in vegetative state. These findings have prognostic potential.