Salt-sensitive hypertension is common in people of African origin, and may be caused by increased transepithelial sodium absorption. The pH of nasal secretions is negatively correlated with the difference in Na(+) concentration between nasal secretions and plasma, and may be a marker of transepithelial sodium absorption. Nasal pH was measured using a probe sited under the inferior turbinate. Measurements of nasal pH were reproducible, with a coefficient of variation of 3.3% for repeated measurements on the same day and of 2.7% between measurements on different days. Nasal pH did not correlate with nasal potential difference, a measure of transepithelial sodium absorption. Nasal pH was significantly lower in 89 black individuals (24 normotensive and 65 hypertensive) than in 51 white individuals (26 normotensive and 25 hypertensive) (black normotensive. 6.44+/-0.08; black hypertensive, 6.62+/-0.05; white normotensive, 6.91+/-0.06; white hypertensive, 6.98+/-0.06), after adjustment for age, gender, current smoking status, body mass index and 24 h urinary sodium excretion (P=0.002), but was not significantly different between the normotensive and hypertensive individuals. Nasal pH was more acidic in black than in white individuals, which may represent generalized up-regulation of sodium transport in black people. However, the lack of correlation between nasal pH and potential difference suggests that nasal pH is, at best, only weakly related to transepithelial sodium absorption. Ethnic differences in nasal pH may be of direct relevance in the airways, as many of the functions of airway surface liquid are dependent on pH.