An exclusion map for the major gene that causes nonsyndromic cleft lip with or without cleft palate, CL(P), in the A strain family of mice is presented. Because of linkage homology between mice and humans, this map should be of value to projects intended to map major human gene loci for CL(P). In both species, the genetic complexity of the etiology of CL(P) necessitates unusual and candidate locus approaches. More than 40% of the mouse genome has been swept. Some candidate regions include mouse chromosomes 12, 18, and 19, and candidate loci on other chromosomes should include Rara, Tgfa, Bmp2b1, and Igf-2.