The periodontal conditions in 19 patients with unilateral cleft lip, alveolus and palate (CLAP) and in 6 patients with bilateral CLAP, were evaluated in 1979 and re-examined in 1987. During these 8 years, these patients were not subjected to any professionally supervised maintenance care program. Pronounced plaque accumulation and high frequency of gingival units exhibiting bleeding on probing were noted in the majority of the patients both in 1979 and 1987, documenting inadequate oral hygiene standards with resulting inflammatory reactions of the periodontal tissues. Progression of periodontal disease over time was assessed as loss of clinical attachment and loss of alveolar bone height. The periodontal destruction was not found to be more severe at cleft sites with a long connective tissue attachment than at control sites not affected by cleft defects. It was concluded that sites with a long supracrestal connective tissue attachment do not seem to be more prone to periodontal destruction, induced by bacterial infection, than sites with a normal length of the supraalveolar fibrous attachment. The results also show that the alveolar bone height, as visualized in radiographs at sites with alveolar defects, is of limited value for the diagnosis of the degree of periodontal destruction at such sites.