The long neck of the giraffe presents a unique problem in the regulation of the systemic arterial blood pressure and in the maintenance of the cerebral circulation. In 1954, Goetz and Budtz-Olsen succeeded in measuring the arterial blood pressure in a standing, unanesthetized giraffe. In this animal, approximately 13 feet tall, the carotid artery mean pressure was found to be 200 mm. Hg at the base of the brain. The present study was undertaken 2 years later as a sequel to this preliminary observation to provide detailed information concerning the circulation of the giraffe. Concomitant studies of respiratory function will be reported separately.