BACKGROUND During the last decade, there have been great strides in the treatment of gingival recession defects, especially with subepithelial connective tissue graft and guided tissue regeneration (GTR) procedures. Gingival recession represents a significant concern for patients. It is necessary to choose the most appropriate procedure in order to obtain more root coverage while avoiding clinical disadvantages. The purpose of this randomized clinical trial was to evaluate the use of a bioabsorbable bilayer collagen membrane with GTR compared to a connective tissue graft in the treatment of gingival recession defects. METHODS Twenty patients each contributing a pair of Miller Class I or II buccal gingival recessions were treated. In each pair, one recession was randomly assigned for treatment with GTR using a bioabsorbable bilayer collagen membrane and the other treated with subepithelial connective tissue graft (CTG). Clinical measurements taken at baseline (D0) and 3 and 6 months post-treatment included recession depth (RD), recession width (RW), probing depth (PD), and clinical attachment level (CAL). RESULTS Data were analyzed using the non-parametric Wilcoxon matched pair test. All results were statistically significant. Both treatments resulted in a significant gain of root coverage (P<0.0001), amounting to an average of 2.80 mm at 3 months in the GTR group and 3.34 mm in the CTG group. At 6 months, the decrease of the mean RD remained statistically significant: 2.70 mm (74.59% root coverage) in the GTR group and 3.19 mm (84.84% root coverage) in the CTG group. The mean RW also decreased from 4.48 mm at D0 to 2.42 mm at 6 months in the GTR group, and from 4.38 mm at D0 to 1.35 mm at 6 months in the CTG group, representing a percentage of coverage of 45.98% and 69.18%, respectively. Mean CAL gain obtained between D0 and 6 months with the GTR procedure and CTG was 3.31 mm and 3.09 mm, respectively, and was significant within groups. At 3 and 6 months, the differences in the results for RD, CAL, and RW were not statistically significant between the 2 groups. However, the difference was significant for PD at 3 and 6 months. CONCLUSIONS The results suggest that a bioabsorbable bilayer collagen membrane can be used in the GTR treatment of human buccal recession defects, with no statistically significant differences between this procedure and connective tissue grafts.