In this study, active Anterior Rhinomanometry (ARM) and Posterior Rhinomanometry (PRM) were performed sequentially by 56 normal British Caucasian adults using an on-line Mercury Electronics NR6D Rhinomanometer. Xylometazoline nasal spray was used as a nasal decongestant before the test. In addition, repented measurements were made on a randomly selected 13 subjects to evaluate the error of the methods. The mean total nasal airway resistance by the anterior method was found to be 0.182 Pa/cm(3)/s at a reference pressure of 150 Pascals, and by the posterior method 0.166 Pa/cm(3)/s at a reference pressure of 75 Pascals. These mean values are similar to those reported by other authors for Caucasians. The errors of the methods were found to be smaller than previously reported (Coefficient of variation, ARM = 6.9%; PRM = 7.7%). The total nasal airway resistance was higher during expiration than inspiration, and higher in women than in men. The ARM values were on an average 9% higher than those of the PRM and the association between the two values was found to be moderate (r = 0.48). The higher ARM mean values could be attributed to inappropriateness of the conventional Ohm's law used in their calculation. For a number of reasons, PRM is considered to be more suitable than ARM for measuring nasal resistance.