Tooth agenesis was investigated in 101 patients with complete unilateral or bilateral cleft lip and palate presenting four third molars. The prevalence was found to be six times higher than in the control group. The most commonly missing teeth were the upper second premolars and the upper lateral incisors. With the exception of one patient, tooth agenesis in the mandible was only found in combination with congenital absence of teeth in the maxilla.