BACKGROUND Premaxillary size in individuals with cleft lip and palate is variable, ranging from a mere nubbin to a large protuberance. The purpose of this study was to evaluate the effect of premaxillary size on craniofacial growth in cleft lip and palate patients. METHODS Premaxillary size was measured using 181 dental casts of bilateral complete cleft lip and palate (BCLP) infants. The infants had no associated systemic malformations, and were approximately one year of age. Data were obtained from the files of the Chang Gung Craniofacial Center. The mean size (mean = 19.3 mm) of the premaxilla and standard deviation (SD = 2.0 mm) were calculated. A sample of 55 subjects was divided into three groups: large premaxilla; [LP; 15 boys, 5 girls; mean age 5.2 years; premaxillary size > (19.3 + 2.0) mm; mean size 22.6 mm]; small premaxilla [SP; 15 boys, 5 girls; mean age = 5.1 years; premaxillary size < (19.3-2.0) mm; mean size = 16.5 mm] and bilateral-median facial dysplasia [B-MFD; 6 boys, 9 girls; mean age 5.1 years; mean size 10.5 mm]. They all had a bilateral cheiloplasty at about 3 months of age and palatoplasty at about one year of age. Lateral cephalograms were taken at about 5 years of age to compare the craniofacial complex among the three groups. RESULTS The LP group tended to have a longer maxilla, longer anterior maxillary height and more protruded maxilla, producing a better interjaw relation and larger overjet. The opposite phenomena were observed in the B-MFD group, and the SP group had results between those of the LP group and the B-MFD group. CONCLUSIONS BCLP patients with large premaxilla had superior maxillary growth (in depth and anterior height) as compared to those with small premaxilla.