A 2-stage topical treatment regimen (AgF followed by SnF2) was used in an attempt to limit caries progression in the primary molars of children participating in a minimal treatment programme. The children lived in an isolated community in western New South Wales (fluoride in water less than 0.2 parts/10(6)) and were from a low socioeconomic background. The progression, over a 24-month period, of 281 established lesions in the approximal and occlusal surfaces of primary molars in 54 subjects (mean age 7.0 years) was determined from bitewing radiographs. Of the lesions studied, the majority (69%) were in dentine at baseline. At 24 months, 74% of the approximal surface lesions and 90% of the occlusal surface lesions that were in enamel at baseline remained unchanged. The greatest change occurred in the approximal surface lesions that were within 1 mm of the pulp at baseline. Only 35% of the lesions required any treatment other than topical metal fluoride therapy during the 24-month period.