A vascular haemostasis device has recently been introduced that allows percutaneous implantation of collagen plugs for haemostatic sealing of puncture sites even under full anticoagulation. This study assessed the incidence of access site complications after collagen plug implantation in patients with percutaneous coronary angioplasty (PTCA) or coronary stenting. Seventy-eight patients with coronary stenting and 231 patients with PTCA were included in a prospective randomized trial comparing collagen plug implantation to conventional haemostasis. Collagen plug implantation significantly reduced median manual compression times from 45 min (quartiles: 35 min, 51 min) to 5 min (4 min, 6 min) after stenting (P = 0.001) and from 27 min (20 min, 32 min) to 5 min (4 min, 6 min) after PTCA (P = 0.0001). After stenting, in 15 of the 37 patients with collagen implants, access site complications occurred (11 pseudoaneurysms, one arteriovenous fistula, three bleedings requiring blood transfusion, four local infections). The complication rate in the control group (17/41) was not significantly different (P = 0.88). After PTCA, three of the 114 control group patients suffered access site complications, while in the corresponding treatment group of 117 patients, complications occurred in 16 (seven pseudoaneurysms, one arteriovenous fistula, six infections, two femoral occlusions, one bleeding with nerve compression; P = 0.0049). In conclusion, the vascular haemostasis device allows rapid sealing of the vascular access site even under full anticoagulation. Its use after PTCA was however associated with increased access site complications, particularly infections, and even after coronary stenting, failed to reduce the incidence of access site complications.