One hundred patients undergoing routine diagnostic or interventional catheterization were randomly assigned to receive either percutaneously applied collagen (group A; n = 50) or conventional pressure dressing (group B; n = 50) for sealing of the femoral artery. Clinical variables were comparable in both groups. The heparin dose was 100 IU/kg in 30 patients and 200 IU/kg in 20 patients of both groups. The average compression time was 4.3 min in group A and 42.3 min in group B (p < 0.001). In group A, 1/50 patients required pressure dressing compared to 50/50 patients in group B. Bleeding was not observed in group A, but was observed in 6/50 patients in group B. The time to ambulation was 6.4 (range, 4-12) h in group A and 21.6 (range, 10-48) h in group B (p < 0.001). Hematomas with a diameter of > 6 cm developed in 4/50 patients in group A and in 11/50 patients in group B (p < 0.05). Blood-transfusions or surgical interventions were not required and there was no loss of ankle pulses in either group. In conclusion, percutaneously applied collagen reduced compression time and duration of bedrest after diagnostic catheterization and PTCA. Despite earlier ambulation, the incidence of bleeding was lower with collagen than with conventional pressure dressing.