Low pH aqueous solutions of citric acid have been used in surgical periodontal therapy mainly for two reasons. It dissolves smear after a relatively short exposure time and it has been claimed to selectively remove root surface-associated mineral exposing collagen to varying degrees. The use of low pH etching agents has recently been challenged in both experimental in vitro and in vivo studies based on their necrotizing effect on the surrounding periodontal tissues. The purpose of the present study was to assess the efficacy of subgingival application of an EDTA gel preparation in removing smear and exposing collagen fibers in root surfaces following non-surgical periodontal therapy. Root surfaces which were root planed did not reveal any patent dentinal tubuli or collagen fibers. This was in contrast to the findings seen after root planing followed by etching, where intertubular surfaces were covered by a dense fibrillar network extending into patent dentinal tubuli. In high magnification these intertubular fibers displayed the cross-striated texture typical for collagen fibers. Etching of root planed surfaces with EDTA may thus enhance the effect of non-surgical root debridement in the same way as has been shown during experimental surgical procedures.