The purpose of this study was to clinically evaluate the effect of citric acid on re-attachment and re-adaptation in conjunction with periodontal surgery. A split-mouth design was used in 10 patients involving 30 quadrants of surgery. A total of 120 teeth were treated. Each quadrant consisted of at least 2 teeth from cuspid to second molar. One quadrant was treated with a modified Widman flap alone while the root surfaces of the contralateral side were also treated with a 3 min application of citric acid. Immediately following hygienic phase and at 3 and 6 months postsurgically, the following measurements were taken in this sequence: gingival index, gingival crevicular fluid flow, plaque index, furcation involvement, level of attachment and probing depth. All the data were statistically analyzed using the paired t-test, chi 2 and Fisher exact probability test. The biometric results showed that both surgical techniques resulted in a loss of attachment in shallow pockets and a gain in deeper pockets. Both techniques resulted in similar amounts of recession and probing depth reduction at 6 months. Gingival index, plaque index and furcation values decreased at 3 and 6 months postsurgically. The gingival crevicular fluid values remained essentially the same up to 6 months postsurgically.