The measurement of oesophageal pressure during maximal sniffs (Poes sniff) is useful to assess inspiratory muscle strength. The aim of this study was to develop a noninvasive test of inspiratory muscle strength based on the sniff manoeuvre. The sniff nasal inspiratory pressure (SNIP) was measured through a plug occluding one nostril during sniffs performed through the contralateral nostril. In 10 normal subjects and in 12 patients with neuromuscular or skeletal disorders, the SNIP reliably reflected the Poes sniff. Nasal mucosa congestion was induced in four normal subjects by nebulization of increasing doses of histamine. The SNIP accurately reflected Poes sniff when nasal congestion was moderate, but failed to do so when congestion was severe. Reference values of SNIP were established in a group of 160 healthy subjects aged 20-80 years. For both men and women, SNIP was negatively correlated with age, and was similar in the sitting and in the supine positions. SNIP was higher than maximal inspiratory pressure (P1 max) in most subjects, but the wide limits of agreement showed that these two methods are not interchangeable but complementary. The SNIP represents a useful noninvasive test of inspiratory muscle strength.