The purpose of this study was to examine whether positive changes in consciousness level after applying a sensory stimulation programme exceed natural recovery. A single experimental group interrupted time series design was used. Subjects were brain-injured patients who were hospitalized at a university hospital in South Korea. The sensory stimulation programme was composed of auditory, visual, olfactory, gustatory, tactile and physical stimulation. Levels of consciousness were evaluated using the Glasgow Coma Scale. The intervention was carried out twice, first for 4 weeks, then a recession period was allowed for 4 weeks, and immediately after this the second intervention was implemented for 4 weeks. Results showed significant alterations in consciousness levels 2 weeks after starting intervention 1. This effect increased gradually and was maintained for 3-4 weeks. However, consciousness levels began to decrease 2 weeks after terminating intervention 1 and this decrement continued until starting intervention 2. The pattern of improvement of intervention 1 could be represented as a gradual onset and temporary duration model. At the beginning of intervention 2, consciousness levels were maintained at a low level. However, they began to increase again after 2 weeks and this increment continued even after terminating intervention 2. Therefore, the effect of intervention 2 could be represented as a gradual onset and permanent duration model. These results suggest that an intervention programme should be applied for more than 1 month to achieve a permanent effect on consciousness levels and that at least 2 weeks are required for any significant effect.