Two main types of membrane barriers are used for bone regeneration, non-resorbable and resorbable. Polytetrafluorethilene non-resorbable membranes have been extensively studied but they require a second surgical step for removal. Although polylactic acid (PLA) resorbable membranes avoid this problem, they have not been sufficiently evaluated on bone defects. The purpose of this pilot study was to compare the healing events of bone regeneration after placement of non-resorbable or resorbable membranes and to evaluate the amount of newly formed bone 2 and 4 months after membrane placement. Mandibular second, third and fourth premolars of four adult mongrel dogs were extracted bilaterally. Two rectangular bone defects (8 mm corono-apical and 12 mm mesial-distal) were created bilaterally 3 months after tooth extractions. Each dog received two resorbable membranes and one non-resorbable membrane; one defect was left untreated. Two dogs were killed at 2 months and the remaining two at 4 months following surgery. Undecalcified sections were obtained and stained with toluidine blue and pyronin G. Histomorphometric analysis was performed using the NIH Image software. Newly formed bone was observed under both resorbable and non-resorbable membranes. The amount of regenerated bone was similar between both treatments at 2 and 4 months after surgery. At 2 months, the newly formed bone was still immature whereas at 4 months some areas of woven bone were observed. The bone formation observed in the untreated defects was significantly lower than that observed in both resorbable and non-resorbable membrane-protected defects. In summary, the present study suggests that PLA membranes can yield good results when used on bone defects while avoid a second surgical procedure.