Fifty-five children and adolescents, 8 to 19 years of age, with moderate or severe asthma, and 28 healthy volunteers, 11 to 16 years of age, were interviewed about oesophageal and bronchial symptoms and investigated with oesophageal manometry combined with pH-reflux tests, an acid perfusion test and an acid clearing test. Oesophageal dysfunction (OD) was significantly more common in asthmatic (60%) than in healthy (14%) subjects (p less than 0.01). Ten of 18 subjects (56%) with frequent nocturnal or morning asthma had a positive acid perfusion test as compared to 16% of patients with less severe asthma (p less than 0.01). Non-allergic asthma was not significantly more related to OD than was allergic asthma. Presence of OD was not related to present beta 2-stimulant or theophylline medication. Symptoms of OD had a sensitivity of 52% and a specificity of 100% regarding OD in the asthmatic subjects. In conclusion, asthma was frequently associated with OD. There is indirect evidence that OD, especially acid hypersensitivity of the oesophagus, can aggravate asthma.