A report on 2820 x-rayfilms of the sinus maxillaris from adults, on 120 x-rayfilms from child-like and youthful patients as a control group and from 301 x-rayfilms from patients with cleft formations to show the aplasia of the sinus maxillaris and frontalis is being given. A aplasia of the sinus maxillaris wasn't found. For the sinus frontalis a aplasia in 11% was found by adults. The one side aplasia was observed by 7.4% and the double-sided by 3.4%, the right-sided aplasia by 4.2% and the left-sided by 3.2%. Patients with cleft formations: The aplasia of the sinus frontalis was found by 55.8%, by the control group in 46.7%. In the age groups 1 to 5 years and 6 to 10 years more double-sided aplasia was found. This result is agree with the results by the control group. The right-sided aplasia is dominant in comparison to the left-sided aplasia in the control group.