Engineered small diameter vascular grafts must closely match mechanical characteristics of native vessels and exhibit stimulus-responsive bioactivity. In this study, mechanical homogeneity of electrospun small diameter polyurethane grafts as well as spontaneous attachment, proliferation, and adhesion molecule expression of endothelial cells (EC) in their presence was studied in vitro. Axial and circumferential tensile strengths were measured and found to be twofold higher in the circumferential direction. EC attachment was easily achieved without precoating the fiber matrix. Stimulation of EC with interleukin-1 beta (IL-1 beta) led to a statistically significant upregulation of the adhesion molecules E-Selectin, ICAM-1, and VCAM-1. Quantification of adhesion molecule expression by means of energy-dispersive X-ray microanalysis revealed no differences in the stimulatory responses of EC cultured on electrospun polyurethane when compared with cells grown on tissue culture-treated cover slips. Summarizing, highly uniform small diameter polyurethane grafts were fabricated and shown to allow spontaneous EC attachment. The synthetic graft surface neither impaired the endothelial response toward IL-1 beta stimulation nor did it adversely affect the regulation of expression of endothelial adhesion molecules. (C) 2009 Wiley Periodicals, Inc. J Biomed Mater Res 93A: 716-723,2010