The aim of the study was to determine the differences in nitrite, in the exhaled breath condensates of healthy children and those children with asthma, cystic fibrosis (CF) and nonasthmatic, episodic cough. Breath condensates were obtained from 66 children (43 males:23 females, 3.1-16 yrs) and included 29 asthmatics, 12 clinically stable CF patients, 12 children with cough but not asthma and 13 healthy volunteers. The collected condensate was assayed colourimetrically using the Griess reaction to determine nitrite concentrations. Patients with CF (median: 5-95% percentiles; 2.02: 0.43-6.37 microM) or asthma (2.10: 0.63-5.45 microM) had significantly higher levels of nitrite compared to healthy subjects (0.41: 0.13-1.83 microM; p<0.05) or subjects with cough (0.75: 0.03-1.75 microM; p<0.05). Airway inflammation, as assessed by the nitrite in breath condensates, is present in children with asthma and cystic fibrosis, but not those children with nonasthmatic, episodic cough. Nitrite can be conveniently, cheaply and rapidly measured in breath condensates of children as young as 3 yrs of age, and may prove useful for the assessment of airway inflammation in children with respiratory disease.