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Objective. Sandstorms frequently cause adverse health effects especially in patients with asthma. The aim of our research was to explore the mechanism of sandstorm-induced asthmatic exacerbation by administering dust aerosol through an environmentally controlled exposure chamber. Methods. Four samples of soil (Ganganagar clay, Bikaner sand, Jaipur sand, and Ganganagar sand) were collected from three sandstorm-prone areas of Rajasthan, the desert state of India. Twenty patients with asthma, who had stable disease with a forced expiratory volume in first second (FEV1) more than 70% of predicted, volunteered to participate in this randomized single-blind placebo-controlled crossover study. The four samples of dust and placebo were administered randomly on 5 study days. FEV1 was measured for the next 60 minutes and the maximal decline in FEV1 (Delta FEV1) from baseline was measured. The samples of dust were also analyzed for particle size and adhesiveness. Results. The maximal decline in FEV1 was observed 15 minutes post-exposure with all dust samples. Mean Delta FEV1 was 0.69 +/- 0.08 liters for Ganganagar clay, 0.52 +/- 0.06 liters for Bikaner sand, 0.39 +/- 0.07 liters for Jaipur sand, and 0.32 +/- 0.04 liters for Ganganagar sand dust aerosol samples. Decline in FEV1 correlated with volume of dust particles with size < 10 mu m (PM10) and adhesiveness of the dust particles. Conclusion. Smaller-size sandstorm dust particles with higher adhesive properties have a greater potential of aggravating asthma.