Several studies have examined the relationship between anorexia nervosa and oral status. However, none has used control subjects. Furthermore, none has examined bacteriological data in these subjects to determine whether dietary restrictions, particularly of carbohydrates, change the levels of Streptococcus mutans and Lactobacillus species. Fifteen female subjects recently hospitalized for anorexia were studied along with fifteen age- and sex-matched control subjects. The parameters examined included salivary pH and flow rate, levels of S. mutans and Lactobacillus spp., DMFT scores, facial and palatal plaque scores, periodontal pocketing, gingival recession and bleeding following gentle probing. Compared with control subjects, anorexics had significantly lower salivary pH (7.1 +/- 0.4 vs 7.6 +/- 0.3, p less than 0.01), more facial and lingual surfaces with plaque scores of 1 (facial plaque 38 per cent vs 18 per cent, p less than 0.01, lingual plaque 47 per cent vs 29 per cent, p less than 0.01), more surfaces with gingival recession (1 mm-7.9 per cent vs 1.8 per cent, p less than 0.001; 2 mm-1.7 per cent vs 0.2 per cent, p less than 0.001; greater than 2 mm-0.6 per cent vs 0.0 per cent, p less than 0.001), more surfaces with bleeding on probing (16.9 per cent vs 6.5 per cent, p less than 0.001) and fewer sextants with CPITN scores of 0 (1.9 +/- 1.5 vs 3.2 +/- 1.0, p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)