Various aspects have been proposed as the cause of otitis media with effusion (OME) in cleft lip and/or palate (CL/P) populations (i.e. abnormal anatomic relation of Eustachian tube (ET) musculature and soft palate; the lack of intact palatal partition; reduction of nasal patency or chronic rhinitis; timing and type of surgery). However, the role of deviated craniofacial skeleton (CFS) in CL/P has been neglected, although the role of the craniofacial development on poor ET function has been advocated in non-cleft children. In this study, we evaluated clinical and cephalometric data of 37 Japanese children with unilateral complete cleft lip and palate (UCLP, 25) or isolated cleft palate (ICP, 12) and compared them to 40 non-deft children, who were proportionally matched for age and sex. Data showed that OME was more often in children with unilateral cleft lip and palate-UCLP (76%) and those with isolated cleft palate-ICP (67%) than non-clefts (10.00%). In addition to a number of skeletal abnormalities (i.e. short dimensions related to the posterior cranial base and backward and upward position of the maxilla) detected in CL/P cases, mastoid depth and height were also shorter in cleft cases than normal subjects. On the other hand, a small tendency to recurrent upper airway infection (RUAI) was observed in cleft cases with OME. Further, it was found that the following differences in the mastoid-middle ear-Eustachian tube (M-ME-ET) system were associated with a tendency to OME in UCLP cases: more horizontal ET in relation to the posterior cranial base; short bony ET; short height and antero-posterior depth of the mastoid air cell system. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.