The aim of this in vivo study was to evaluate the influence of 5- to 6-year-old direct composite additions on the marginal periodontal tissues. Composite additions were directly placed on 79 intact maxillary anterior teeth in 19 patients (12 to 19 years) by one operator using an ultrafine midway-filled densified resin composite. All patients were recalled 5 to 6 years later for a periodontal evaluation. Plaque index, gingivitis index, and probing depth were measured at the buccal-approximal sites of all unilaterally restored teeth (n = 51). An intra-individual comparison was made between the periodontal health of the treated versus the intact sites. The plaque index (P = 0.029) and gingivitis index (P = 0.008) were significantly higher for the treated sites compared to the intact sites. The difference in probing depth nearly reached the level of significance (P = 0.059). In conclusion, 5-to 6-year-old direct composite additions have a negative influence on marginal periodontal health, which consisted of increased plaque retention, gingival inflammation, and periodontal destruction. J Periodontol 1998;69:422–427.