Objective: Major sand storms are frequent in the Middle East. This study aims to investigate the role of air particulate matter (PM) level in acute asthma in children in Riyadh, Saudi Arabia. Methods: An aerosol spectrometer was used to evaluate PM < 10μm in diameter (PM 10 ) and PM < 2.5 μm in diameter (PM 2.5 ) concentrations in the air every 30 minutes throughout February and March 2012 in Riyadh. Data on children 2-12 years of age presenting to the emergency department of a major children′s hospital with acute asthma during the same period were collected including their acute asthma severity score. Results: The median with interquartile range (IQR) levels of PM 10 and PM 2.5 were 454 μg/m 3 (309,864) and 108 μg/m 3 (72,192) respectively. There was no correlation between the average daily PM 10 levels and the average number of children presenting with acute asthma per day (r = -0.14, P = 0.45), their daily asthma score (r = 0.014, P = 0.94), or admission rate ( r= -0.08, P = 0.65). This was also true for average daily PM 2.5 levels. In addition, there was no difference in these variables between days with PM 10 >1000 μg/m 3 , representing major sand storms, plus the following 5 days and other days with PM 10 < 1000 μg/m 3 . Conclusion: Sand storms, even major ones, had no significant impact on acute asthma exacerbations in children in Riyadh, Saudi Arabia. The very high levels of PM, however, deserve further studying especially of their long-term effects.