Guided tissue regeneration procedures are intended to selectively favor healing by the periodontal ligament tissues. However, in most studies of the efficacy of guided tissue regeneration, nonresorbable barriers and membranes have been used, necessitating their surgical removal after a time. The present study employed a resorbable collagen barrier to treat Class II function invasions. The results of this treatment were compared with the results of conventional therapy. For most clinical parameters, there was no statistically significant difference in the results of treatment with or without collagen membranes. Sites treated with a collagen barrier did exhibit statistically significant improvement in probing depth and horizontal osseous support; however, these findings cannot be attributed entirely to the placement of the collagen membrane.