Pharyngeal wall inspiratory collapse (PWIC) is a dynamic obstruction of the air column proximal to the glottis during inspiration. Our objectives were to assess PWIC's incidence and its contribution to the symptoms of upper airway obstruction (UAO), and to propose indications for intervention. In a retrospective review of consecutive endoscopic evaluations and clinical data of 108 infants with UAO, PWIC was diagnosed in 50 infants (46%). The most common presenting symptom was apnea (52%). The PWIC was accompanied by 2 to 7 synchronous airway abnormalities, most frequently laryngomalacia (78%). Generalized hypotonia was the most common associated systemic finding (80%). Severe PWIC cases required bi-level positive airway pressure (BiPAP). The severity of PWIC, measured by a newly developed classification, was positively correlated to apnea (p < .05) and the need for BiPAP (p < .054). Spontaneous recovery occurred within 36 months. The incidence of PWIC among infants with UAO is high, and its role in UAO deserves greater recognition. Better diagnosis of PWIC will improve the treatment of UAO.