A cross-sectional clinical study showed that the prevalence of caries among Indonesian soldiers was low, compared with that found in corresponding Western populations. Also, the progression of caries was very slow, and caries was limited almost exclusively to the occlusal surfaces of the teeth. Among officers, the prevalence of caries was lower than it was among other ranks of the same age. The low general prevalence of caries among Indonesian soldiers may be related to diet. Rice was the major source of carbohydrate for the soldiers, and their sucrose consumption was 10 kg per person per year. Their drinking water contained a low concentration of fluoride (0.1 ppm). In spite of massive accumulations of calculus, the periodontal health of young soldiers (less than 26 yr) was also good. Among those in higher age groups, however, periodontal health had deteriorated, but even in a group aged 40-46 yr, no teeth had been lost as a result of periodontal disease. Among officers, periodontal health was better than it was amongst other ranks of corresponding age. The officers had been accustomed to brushing their teeth regularly, whereas the other ranks had not. It thus appears that toothbrushing may help to preserve periodontal health, even when large amounts of calculus are present on the teeth and there is no opportunity for it to be removed regularly by a dentist.