This article describes the design of an intercenter comparative study of treatment outcome in the treatment of children with a unilateral complete cleft of the lip and palate. The rationale and aims of this study are defined and treatment schemes of the participating centers are described. The findings are presented in a series of three papers (Parts 2, 3, and 4) dealing with the comparison of craniofacial form, dental arch relationships, and nasolabial appearance. In Part 5, conclusions and general recommendations regarding future research are discussed.