The development and progression of atherosclerotic disease in saphenous vein grafts (SVGs) following coronary artery bypass surgery (CABG) are often without symptoms. Four-slice CT is a non-invasive imaging technique reliable for assessing SVG patency. This study utilised CT to assess temporal progression of patency in asymptomatic patients. A four-slice CT scanner was used employing standard techniques. Analysis of the reconstructed images was performed offline by two experienced operators blinded to patient details. The primary aim was vein graft patency. 130 asymptomatic subjects were studied. The mean time from CABG was 7.3 years (range, 15 days to 21 years 9 months; standard deviation (SD), 4.4 years). 294 of the 305 SVGs were suitable for assessment of patency. The overall occlusion rate for assessable grafts was 23.5%. Occlusion rates for grafts <1 year old was 12.5% (2/16), 20.7% (42/203) for grafts 1-10 years old, and 33.3% (25/75) for grafts >10 years old. In conclusion, significant occlusion of SVGs occurs early after CABG in asymptomatic patients. Four-slice CT has the potential for the non-invasive assessment of individuals after surgery.