In this report on the findings of a baseline study designed to monitor changes in the prevalence of dental caries in 12-yr-old children in Dar es Salaam and Nairobi, the details relating to the pattern of carious attack on particular tooth and surface types are described. In both populations molars accounted for over 90% of all affected teeth and in both groups first molars were more affected than second molars. Very few anterior teeth were affected in either population, though caries of the incisors and canines accounted for a greater proportion of affected teeth in Nairobi (3.4%) than in Dar es Salaam (0.6%). Significantly more mandibular first and second molars were affected in Dar es Salaam than in Nairobi, though in Nairobi the maxillary first molars were more affected than in Dar es Salaam. Occlusal surfaces were the most common site for caries in both populations. With the exception of buccal surfaces, smooth surface caries tended to be higher in Nairobi than in Dar es Salaam. Dar es Salaam children had, however, a significantly higher mean DFS score for occlusal surfaces. The preponderance of occlusal caries indicates that relatively simple restorative care is required to meet the needs of the two populations, and it is suggested that such care could be largely provided by auxiliary dental personnel.