Inspiratory muscle strength is an important variable in patients with neuromuscular or skeletal disorders. It is usually assessed by measuring maximal inspiratory pressure (PI(max)), but this test may prove difficult for some patients, and low values may originate from incomplete effort or air leaks. We assessed the usefulness of the novel sniff nasal pressure (Pn(sn)) test in 126 patients with a neuromuscular or a skeletal disorder, aged 5 to 49 yr. Pn(sn) was measured in an occluded nostril during maximal sniffs performed through the contralateral nostril. All patients performed the Pn(sn) maneuver easily, whereas 10 young and weak patients with neuromuscular disorders could not perform the PI(max) maneuver. Data were analyzed for the 116 patients who could perform both tests (92 patients with neuromuscular and 24 with skeletal disorders). When expressed as percents of the predicted values, Pn(sn) was similar to PI(max) in patients with neuromuscular disorders (54 +/- 25% predicted [mean +/- SD] versus 52 +/- 24% predicted), and was higher than PI(max) in patients with skeletal disorders (70 +/- 25% predicted versus 61 +/- 27% predicted, p < 0.05). Pn(sn) appeared to be the main determinant of VC in patients with neuromuscular disorders, whereas the Cobb angle and PI(max) were the main determinants of VC in patients with skeletal disorders. We conclude that inspiratory muscle strength can be easily assessed with Pn(sn) in children and adults with various neuromuscular and skeletal disorders. This new muscular parameter appears particularly useful in neuromuscular disorders, in which it represents a major determinant of VC.