A tissue pressure model was developed to provide a possible physiologic basis for the manifestation of the cranial rhythmic impulse (CRI). The model assumes that the sensation described as the CRI is related to activation of slowly adapting cutaneous mechanoreceptors by tissue pressures of both the examiner and the subject, and that the sources of change in these tissue pressures are the combined respiratory and cardiovascular rhythms of both examiner and subject. The model generates rhythmic impulses with patterns similar to those reported for the CRI. Also, a significant correlation was found between frequencies calculated from the model and published values for CRI obtained by palpation. These comparisons suggest that the CRI may arise in soft tissues and represents a complex interaction of at least four different physiologic rhythms.