A recirculating in vitro perfusion system was used to assess the effect of albumin precoating on the thrombogenicity of Dacron vascular grafts. A complete analysis of platelet activation was carried out, involving platelet count, release, adhesion and aggregation. Fibrin formation was assessed by measuring fibrinogen levels and fibrinopeptide A production; leucocyte interaction was analysed by measuring total leucocyte count as well as an analysis of cell adhesion to the surface by scanning electron microscopy. The platelet count decreased progressively with perfusion time for Dacron until by 30 min, it had declined to 69% +/- 2% of baseline. The platelet count did not, however, change significantly from baseline when albumin-coated Dacron was tested. Release of platelet factor 4 and beta-thromboglobulin at 180 min for Dacron was 37.8 +/- 29.8 times and 66.9 +/- 18.2 times baseline, respectively, while albumin coating caused significantly less (P less than 0.03) platelet release. Albumin coating diminished coagulation activation and fibrinopeptide A formation. The total leucocyte concentration decreased significantly for Dacron by 180 min, while that for albumin-coated Dacron did not change significantly from baseline levels. Albumin coating produced a film-like covering over the Dacron. For Dacron, there were numerous leucocytes and platelets adherent to the surface, whilst cellular deposition was minimal upon the albumin-coated surface. Thus, albumin coating improved the short-term blood compatibility of Dacron by all of the methods employed in this study.