The lower lip was examined in 397 children with isolated cleft palate (CP), in 518 cleft lip children with or without cleft palate (CL(P)) and in 1000 noncleft children. Familial occurrence of clefts, other concomitant anomalies and the type and extension of the cleft were determined from the child's medical history. A total of 323 orthopantomograms, taken at the ages of 6-12 years, were available in the detection of hypodontia of the permanent teeth excluding the third molars in the CP group. The incidence of lower lip sinus and microforms (conical elevations, CE) was noted. The incidence of sinuses was 2.3% in the CP group, 2.5% in the CL(P) group and 0% in the noncleft group. The corresponding figures for CE were 39.3%, 0.8% and 0.7%, respectively. In the CP group with CE, the familial occurrence of clefts was statistically higher (30.0%) than in the group without CE (20.7%). The corresponding figures for hypodontia were 40.7% and 24.7%, respectively. Conical elevations are cleft palate related disturbances in the development of the lower lip. At least in certain cases the CE do represent microforms of the sinus syndrome. Thus the question arises: do the CE always represent microforms of the Van der Woude syndrome, or are they only pathogenic similarities of a variable etiology?