The present study was designed to quantitatively assess lip pressure changes following cleft lip repair in infants with unilateral cleft lip, alveolus, and palate. Lip pressure measurements were taken using an electronic transducer system developed especially for this study. Lip pressure was monitored from 3 months (preoperatively) through 2 years of age in cleft and normal control children. Findings from the present study confirm the hypothesis that lip repair in infants with unilateral cleft lip and palate significantly increases lip pressure and that increased lip pressure remains significantly higher than in normal control children for the 2-year duration of the study. Thus increased lip pressure when the palate is unrepaired has to be considered as a factor modulating subsequent craniofacial growth.