Previous studies have demonstrated the potential beneficial effects of post-surgical rinsing with 0.2% chlorhexidine. In the present investigation a new chlorhexidine formulation (Peridex) (CHx) and concentration (0.12%) was evaluated clinically to determine if similar effects could be detected from the use of the new product and treatment regimen. A double blind, randomized, placebo-controlled study was carried out in 40 patients during a 6 week period. Patients who had moderate periodontitis (AAP Class III) received osseous periodontal surgery in one quadrant. Each surgical site received periodontal dressing and patients were given a placebo or CHx mouthrinse to be used twice each day. Compared to placebo, CHx significantly reduced plaque at all examinations (54.4% reduction over placebo at 6 weeks, P less than 0.05). Visible plaque (PlI greater than 2) in the CHx group was reduced by 99% over the placebo group at 6 weeks and at 4 weeks post-surgical, gingival inflammation scores were significantly lower in the CHx group (17% reduction over the placebo at 4 weeks, P less than 0.05). Gingival bleeding scores (GI greater than 2) were significantly lower in the CHx group at 4 and 6 weeks (41% and 40% reduction over the placebo group, P less than 0.05). Probing pocket depth and attachment level changes were not significantly different between both groups. Epithelialization rates and pain assessment demonstrated consistently better results in the CHx group, although differences were not statistically significant. Use of 0.12% chlorhexidine immediately following periodontal surgery, for 6 weeks, has been shown to be a clinically effective adjunct providing enhancement of the post-surgical management of periodontal surgical patients.