The purpose of this study was to determine the variability of laboratory nasal function tests in 26 patients (18 female) with seasonal allergic rhinitis (SAR) (mean age 38.1 years). Their usual medication for SAR was withheld for 2 separate one week washout periods, separated by at least 2 weeks, in order to produce clinically significant nasal airflow obstruction. Measurements were made on both occasions for nasal nitric oxide (NO), nasal peak inspiratory flow (nPIF), oral PIF (oPIF), nasal forced inspiratory flow rate in 1 second (nFIV1), oral FIV1 (oFIV1). The respective nasal-oral ratios for FIV1 and PIF were also determined. The intra-individual coefficient of variation was: NO = 14%, nFIV1 = 4%, nFIV1/oFIV1 ratio = 10%, nPIF = 8% and nPIF/oPIF ratio = 12%. Linear regression analysis showed significant (p < 0.05) correlations between nPIF and nFIV1 (R2 = 0.45) and between nPIF/oPIF and nFIV1/oFIV1 (R2 = 0.20). In conclusion, there was a good correlation between the two methods of nasal inspiratory flow, although FIV1 had a lesser degree of variability.