In patients with clefts of the secondary palate, the effect of surgical reconstruction was studied from the time of the palate repair, at the age of 18-24 months, to the age of 5 years. The material comprised 99 children (37 boys and 62 girls). The material was grouped according to the antero-posterior size of the cleft. The changes of the maxillary dimensions were studied on the casts by linear measurements. The occlusion was analysed by descriptive and numerical methods. In the deciduous dentition the smallest intercanine and intermolar dimensions were recorded in patients with large palatal clefts. A the age of 5, the frequency of anterior crossbite was 38% in patients with large palatal clefts, compared with 19--21% in patients with smaller clefts. In boys with cleft palates, the frequency of anterior crossbite was 13% higher than in girls, in spite of the fact that in the material the incidence of large palatal clefts was lower in boys than in girls. In cases of large clefts of the secondary palate, the incidence of anterior crossbite was 12.5 times higher than in a material of non-cleft patients of the same age.