Recent interest in the local delivery of antimicrobial and anti-inflammatory agents has stimulated interest in the efficacy of various treatment regimens. Chlorhexidine gluconate (CHX) delivered daily by home-applied marginal irrigation as a 0.04% solution in combination with a single professional irrigation of 0.12% CHX was tested over a 3-month period. Sixty periodontal maintenance patients each having at least 2 pockets greater than or equal to 4 mm probing depth, and bleeding on probing were assigned to either Group 1: one professional subgingival 0.12% CHX (Peridex) irrigation (Perio Pik) followed by adjunctive daily home marginal 0.04% CHX irrigation (Pik Pocket); Group 2: one professional subgingival 0.12% CHX irrigation followed by adjunctive daily home marginal water irrigation; Group 3: one professional subgingival water irrigation followed by adjunctive daily home marginal water irrigation; or Group 4: control. At baseline and 3 month visits, subgingival plaque samples were taken from 2 sites per patient. Cultural microbiological analysis was performed using non-selective and selective media. Plaque Index, Gingival Index, pocket probing depths, and gingival recession were assessed. Scaling and root planing (supportive periodontal treatment) was provided for each patient followed by subgingival irrigation as outlined above. At 3 months the Gingival Index and pocket probing depths were both significantly reduced (P less than .05) in all irrigation groups compared to baseline. There were no significant changes in clinical parameters in the control group from baseline to 3 months. In Group 1 the GI was significantly reduced (P less than .05) compared to Group 4 at 3 months.(ABSTRACT TRUNCATED AT 250 WORDS)