Subjective nasal obstruction is common among users of continuous positive airway pressure (CPAP). The aim of this study was to measure the acute effect of CPAP on nasal resistance and nasal symptoms in awake normal subjects. Twenty-four healthy CPAP-naive adults (8 males, 16 females; mean age 30, SD 14 years underwent a randomized controlled crossover study comparing nasal CPAP (8 cm H2O) for 6 hours on one occasion and the control condition (nasal mask without CPAP) on the other. Nasal resistance measurements (posterior active rhinometry) before and after the test exposure were similar on both test days. Nasal resistance during CPAP exposure (2.04 SD 0.72 cmH2O/L/s) was significantly lower than on control (2.67 SD 1.07 cmH2O/L/s) - mean difference 0.66 cmH2O/L/s, 95% C.I. 0.19 - 1.13 cmH2O/L/s). The gradient in pressure from CPAP mask to posterior naris during CPAP exposure varied from 1.6 to 2 cmH2O but was not significantly different between time points. Subjective nasal symptom scores and peak nasal inspiratory flow rates did not change significantly on either test day. We conclude that in awake CPAP-naive normal subjects, acute CPAP exposure is associated with a reduction in nasal resistance as compared with the control condition, but is not associated with an immediate post-CPAP change in subjective or objective nasal resistance.