Objectives – Atherosclerosis is a chronic disease of the vasculature that involves a complex interplay between numerous components and products of the blood and the arterial wall. One important anti-atherosclerotic and anti-thrombotic product of the arterial wall is prostaglandin I₂ (PGI₂)¹. Currently, vein grafts remain an important choice of conduit for coronary artery bypass surgery in atherosclerosis, but because of poor long-term patency ² and the lack of reliable interventions to prevent vein graft failure the idea of “designer” bypass vessels is attractive. Here we have investigated, using rat cells, the possibility of selecting populations of vascular smooth muscle cells (VSMCs) with characteristics favourable for the production of vascular media, focusing upon the biosynthesis of PGI₂. Methods – Multiple monoclonal populations of VSMCs were derived from WKY 12-22 rat VSMCs by dilute plating and then characterised for their morphological characteristics and their production of PGI₂. Selected clonal cell types were then further investigated for their influences on platelet aggregation, using light transmission aggregometry³, and adhesion, using the conversion of p-nitrophenol phosphate to p-nitrophenol by platelet acid phosphatase⁴, in a 96-well plate reader. Results – Morphologically distinct spindle-type VSMC clones produced greater amounts of PGI₂ than epithelioid-type clones (Figure 1). Spindle clone 7 was also found to inhibit both platelet aggregation (Figure 2) and platelet adhesion(data not shown) in response to adenosine diphosphate (0.1-30μM), arachidonic acid (10–1000μM), collagen (0.1-30μg/ml), adrenaline (0.001-100 μM), ristocetin (0.2-3.0mg/ml), TRAP-6(0.1–30μM), and U46619 (0.1-30μM). Conclusions – These results demonstrate that clonal VSMC populations with favourable characteristics can be isolated. Such defined, pure VSMC populations could potentially be used to produce vascular grafting media.