Although inflammation is an important component of atherosclerosis, it is unknown whether inhaled corticosteroids (ICS) as anti-inflammatory drugs prevent atherosclerosis. In the present study, carotid atherosclerosis was evaluated by ultrasonography in 150 asthmatic patients who had been regularly treated with ICS, and in 150 matched nonasthmatic controls, with an assessment of atherosclerotic risk factors. Carotid intima-media thickness was significantly lower in the asthmatic patients than in the controls. The prevalence of carotid plaque tended to be lower in the asthmatic patients than in the controls. Defined carotid atherosclerosis was diagnosed in 51 of the asthmatic patients, who were older, with a higher prevalence of males, a higher prevalence of dyslipidaemia and a lower mean daily dose of ICS than the 99 patients without carotid atherosclerosis. Stepwise multiple logistic regression analysis identified age, male sex and dyslipidaemia as positive risk factors for carotid atherosclerosis. The mean daily dose of ICS was a negative risk factor. Carotid atherosclerosis is reduced in asthmatic patients treated with ICS compared with matched controls. This study suggests that ICS may have protective effects against atherosclerosis.