BACKGROUND Exhaled-fraction-of-nitric-oxide (FeNO) norms are absent in healthy elderly North-African subjects. OBJECTIVE i) to identify FeNO influencing factors of elderly Tunisians older 50 years and more; ii) to assess the applicability of some published FeNO norms for elderly in local population; iii) to set-up FeNO norms and to prospectively evaluate their validity in two elderly validation-groups (healthy and asthmatic subjects). METHODS A convenience sample of healthy and asthmatic elderly Tunisians was recruited. Subjects responded to a medical questionnaire and then FeNO levels were measured by an online method (Medisoft, Sorinnes (Dinant), Belgium). Clinical, anthropometric and spirometric data were collected. Three groups of subjects were identified: group I (healthy-elderly; n = 100, 57 females); group II (healthy-validation; n = 17, 4 females) and group III (asthmatic-validation; n = 10, 9 females). ANOVA was performed to compare the three groups' data. RESULTS No significant factor, among those evaluated, influenced Tunisian elderly FeNO values. The available published FeNO norms did not reliably predict FeNO in Tunisian elderly population. The mean ± SD (minimum-maximum) of FeNO (ppb) for group I was 14 ± 6 (3-34). For Tunisian people, each elderly FeNO value higher than 34 ppb will be considered as abnormal. There was no statistical significant difference between FeNO (ppb) mean values of group I and groups II (15 ± 8) or III (18 ± 13). No subject of group II had a FeNO value higher than 34 ppb. Thirty percent of group III subjects had a FeNO value higher than 34 ppb. CONCLUSIONS In practice, FeNO value of more than 34 ppb is considered abnormal in elderly Tunisian population.