The investigation was undertaken to evaluate the effect on the periodontal conditions of fixed unilateral bridges which had been in the mouth 1 to 3 years. Seventy‐three bridges in 73 patients (50 women, 23 men) were examined. One group of 35 individuals had been instructed in methods for improving their oral hygiene, whereas another group (38 individuals) had not.In all, 146 abutment teeth were examined. An equal number of homologus teeth in the same patients served as controls. The gingival state and oral hygiene were recorded according to index systems proposed by Löe and Silness (1963) and Silness and Löe (1964). Pocket depth measurements were made as explained by Glavind and Löe (1967). The location of the crown margins of the bridge retainers was recorded according to a Margin Index System proposed by the author. The distribution of soft deposits and the location of gingivitis were similar around the abutment teeth and the homologous teeth. The average pocket depth of the abutment teeth was not deeper than that of the controls. In areas with crown margins below the gingival crest, more severe gingivitis was registered than in the control areas. The periodontal conditions were better in the individuals who had been instructed to practice oral hygiene measures as compared to the non‐instructed individuals. Possible reasons why soft deposits remain undetected on clinical examination of subgingival restorations are discussed. It is suggested that the gingival inflammation around the abutment teeth and the homologous teeth is caused by the usual bacterial mech