This study was designed to investigate the effect of missing teeth, prosthesis and malalignment on the smile. The full smile photographs of 145 Korean adults(male 114 : female 31) were taken and classified by the lip pattern, the relationship between the lip and the teeth, and the number of teeth displayed in a smile. Besides, the esthetic smile score were estimated by five dentists. Obtained data were compared and analyzed. The results obtained were as follows : 1. The esthetic level of missing teeth group and malaligned group was lower than that of the normal group. 2. The esthetic level of prosthesis group had no difference with that of the normal group. 3. The Number of teeth displayed in a smile had the most effect on the esthetic level in each experimental group.