Guided tissue regeneration (GTR) techniques are increasingly used for the treatment of periodontal defects, or in conjunction with dental implant procedures. As adhesion of bacteria to barrier membranes used in these techniques may lead to failure, a prerequisite for treatment success is an infection-free healing process. The present study examined the adhesion of 3 periodontal pathogenic bacteria: Actinobacillus actinomycetemcomitans, Treponema denticola and Porphyromonas gingivalis, to 3 barrier membranes: Collagen, (Biomend) PTFE, (TefGen-FD) and e-PTFE, (Gore-Tex). The membranes were incubated with 3[H]-thymidine labeled bacteria, and the number of adherent bacteria was calculated using a scintillation counter. The effect of albumin coating on bacterial adherence to the membranes was also studied. Bacterial adherence to the membranes was further examined by scanning electron microscopy (SEM). The results show that the adherence of all bacterial strains to collagen membranes was significantly higher than to the other membranes tested. Precoating of the membranes with albumin did not change the bacterial adherence significantly. These findings are of importance in evaluating the ability of periodontal bacteria to colonize and infect different types of barrier membranes.