OBJECTIVE The present cross-sectional epidemiologic study was to determine the dynamics of occlusal caries in permanent molars and premolars depending on the occlusal morphology. METHODS The study included 960 children aged 7 to 14 years recruited randomly from schools in Plovdiv selected at random. The data were registered in a statistical form. Occlusal caries was diagnosed using Espelid's diagnostic scale, and the occlusal morphology was studied using Hirano's classification. Alternative analysis was used in the statistical analysis of the results at a level of significance P < 0.05. Excel 2003 was used for graphic presentation of results. RESULTS The study show an age dependent increase of the carious occlusal surfaces and decrease of the deep fissure surfaces while the occlusal surfaces with shallow fissures of the first and second permanent molars remain unchanged. Caries develops mainly on occlusal surfaces with deep fissures. The decrease of the deep fissures occurs probably at the expense of the increase of the occlusal surfaces with shallow fissures of the first and second premolars. We also found that first and second premolars tend to be slightly affected by occlusal caries between 9 and 14 years of age. The results of the study suggest that occlusal morphology must be taken into consideration in developing a strategy for prevention of occlusal caries in childhood.