Root planing is an effective method of treating both moderate and severe periodontitis. Predictable and significant improvement in bleeding scores, probing pocket depths and probing attachment levels have been demonstrated by a number of different research groups. Significant positive changes in the subgingival microflora are induced. These improvements can be sustained for longer periods of time if adequate supragingival plaque control is achieved. It is important to realize that the research to date excludes the effects of therapy on furcation pockets. Results of conservative therapy in this critical area remain to be studied.