Abdominal obesity increases the risk of clinical atherosclerotic diseases, but whether it accelerates the progression of preclinical atherosclerosis is unknown. We studied whether waist-to-hip ratio (WHR) and waist circumference are associated with 4-year increase in indicators of common carotid atherosclerosis, assessed by B-mode ultrasonography, in 774 Finnish men aged 42-60 years without atherosclerotic diseases. Men with WHR of <0.91, 0.91-0.96 and >0.96 (thirds) had increase in maximal intima-media thickness (IMT) of 0.230, 0.255 and 0.281 mm/4 years (P=0.007 for linear trend; P=0.025 for difference) and plaque height of 0.241, 0.254 and 0.291 mm/4 years (P=0.005, P=0.013) adjusting for age, body mass index and technical covariates. Men with waist circumference of <85, 85-93 and >93 cm (thirds) had increase in maximal IMT of 0.227, 0.251 and 0.290 mm/4 years (P=0.011, P=0.035) and plaque height of 0.229, 0.263 and 0.296 mm/4 years (P=0.003, P=0.013). These associations were stronger in men with high (> or =3.8 mmol/l) than lower serum LDL cholesterol (P<0.05 for interaction). This is the first documentation that abdominal obesity is associated with accelerated progression of atherosclerosis, and supports the view that it is an important cardiovascular risk factor. This study emphasizes the role of avoiding abdominal obesity to prevent atherosclerotic diseases.