Both the nasal cycle and postural asymmetries between the lateral halves of the body will cause the patent cavity of the nasal airway to change sides. Therefore, the cycle might result from adjustments of posture during prolonged periods of nasal resistance measurements. Posterior rhinometric measurements of unilateral nasal resistance were made three times for 5 to 7 hours on a patient in whom 11 periods of lateral recumbency had not induced nasal resistance changes. A nasal cycle was observed. It is concluded that the cycle is not the product of asymmetrical body pressures.