To confirm whether or not the alar cartilage of the unilateral cleft lip nose is primarily hypoplastic as compared with the noncleft side, 35 unilateral cleft lip nasal patients who had no previous nasal surgery underwent direct measurement of the lateral crus of alar cartilage on both sides during their nasal tip plasties. Both lower lateral cartilages were dissected freely, and the thickness was measured at the intercrural, middle, and distal portions. The width was measured at the widest portion, and the length was measured from the intercrural point to the distal end. Two-mm-punch biopsies were obtained from each cartilage for histologic study. The lateral crus of the cleft side was no smaller than that of the noncleft side. Histologically, no difference was ascertained. In conclusion, we think the lateral crus of the alar cartilage of the cleft side is not hypoplastic. Therefore, external factors such as soft-tissue defect or external abnormal vector force are more attributable than intrinsic factors to the development of cleft lip nasal deformity.