Guided tissue regeneration procedures using resorbable membranes have become accepted therapy for treating periodontal defects. Resorbable collagen and synthetic polylactide and polyglycolide copolymer membranes have been found to support regeneration and preclude the need for surgical removal. This study was undertaken to assess and compare the initial attachment of human gingival fibroblast cells to four collagen-based membranes (fascia lata, fascia temporalis, dura mater, and Type I bovine collagen) and a synthetic polylactic acid-based membrane (resolut®). Human gingival fibroblasts were grown from explants of normal tissue obtained during surgical reduction of retromolar tissues. Membrane specimens were placed in separate culture wells and incubated with fibroblasts for one hour. The number of adherent cells was evaluated by light microscopy using an ocular grid system and detailed examination was performed by scanning electron microscopy. The results of evaluation by light microscopy indicated that initial cell attachment was significantly less in the polylactic acid-based membrane group than in the collagen-based membrane groups (P<0.01). However, no significant differences were found among the collagen membrane groups in terms of fibroblast attachment (P>0.01). Scanning electron microscopy examination of fibroblasts cultured directly on barrier membranes indicated that the collagen-based membranes appeared to facilitate cell attachment, whereas the polylactic acid-based membrane exhibited a morphology that was not conducive to attachment of human gingival fibroblasts. Based on these limited in vitro results, it appears that collagen-based membranes offer greater potential than polylactic acid-based membranes for guided tissue regeneration at surgical sites. (J. Oral Sci. 41, 57-60, 1999)