Objective. To establish the levels of dental caries, bacterial dental plaque, gingivitis and caries-related microflora in children with glycogen storage disease (GSD). Patients with GSD are treated with regular intakes of glucose polymer and uncooked cornstarch to prevent hypoglycaemia. Dental health data are scarce. Study Group. The study group comprised 21 children with GSD attending the Great Ormond Street Hospital for Children. Outcome Measures. These included the number of decayed, missing and filled teeth, and surfaces in both the primary and permanent dentitions, plaque and gingivitis scores. Both plaque and saliva were collected from each child and cultured for Mutans streptococci, Lactobacilli and Candida.Results. The study group included 13 boys and eight girls, aged from 2·7 to 15·5 years. Four of the 21 children had some caries experience. The mean dmft was 0·5 and the mean DMFT, 0·06. Mean plaque and gingivitis scores were 4·8 and 5·9, respectively, for plaque and gingivitis adjacent to the primary teeth, and 11·6 and 12 for those related to permanent teeth. Conclusions. Only a small proportion of the children had caries experience but most were found to have plaque associated with both primary and permanent teeth. Preventive care should be targeted to improve plaque control thus minimizing the risk of developing periodontal disease as adults.