The purpose of this study was to estimate the prevalence of malocclusion in deciduous and permanent dentition of schoolchildren enrolled in public and private schools in the city of Sao Paulo, Brazil, in 1996. Occlusal conditions were classified as normal, mild, and moderate/severe according to World Health Organization criteria. The results refer to 985 schoolchildren ages five and 12 years. Prevalence of malocclusion was high, increasing from 48.97 ± 4.53% in the deciduous dentition to 71.31 ± 3.95% in the permanent dentition. The proportion of moderate/severe malocclusion was nearly twice as great in the second dentition (OR = 1.87; 95% CI = 1.43-2.45; p < 0.001). No significant difference was observed according to gender or public vs. private school. Statistically significant differences were associated with ethnicity, indicating the complexity and diversity of occlusion in the population and suggesting the need for longitudinal studies.