The International Study of Asthma and Allergies in Children (ISAAC) highlighted the presence of wide variations in asthma prevalence between and within countries. The aim of this study was to determine the changes in the prevalence of asthma and its symptoms across the different regions of Oman. Methods: Two cross-sectional surveys were conducted as part of ISAAC phases I (995) and III (200) in two age groups (6-7 and 3-4 years) from nation-wide samples of Omani school children, with 7,067 participants in 995 (3,893 young and 3,74 older group) and 7,879 participants in 200 (4,26 young and 3,753 older group). Results: Over the period of six years, the Sharqiya (Eastern) region continued to have the highest prevalence of self-reported asthma diagnosis and all asthma symptoms in both age groups, with a significant increase in the prevalence of wheeze in the past 2 months (from 8.7% to 3.8%; p=0.002) and asthma diagnosis (from 3.8% to 7.8 %; p=0.046) in the young group, and a significant increase in night cough (from 2.6% to 27.8%; p=0.039) in the older group. All other regions had lower prevalence rates in 995 in both age groups, and showed either no significant change or a decline in one or two of the self-reported asthma symptoms. The prevalence of asthma diagnosis among wheezy children remained unchanged across all regions. In addition, asthma under-diagnosis remains a problem with only 60% of children with severe wheeze reporting asthma diagnosis in both surveys. Conclusion: The geographic variation in the prevalence of self-reported of asthma symptoms among Omani school children persists with further increase in the Sharqiya region. The findings also suggest under-diagnosis and/or poor recognition of asthma which had not improved over time.