The causative actors of shoulder dislocation are variable and complex. Among these factors, the authorsstudied retrospectively the significance of G/H ratio in three groups; recurrent dislocationk traumaticdislocation and normal contrast group. The results were as follows: 1. The mean value of G/H ratio was 74.1±4.7%in 59 cases of recurrent dislocation, 75.9±3.2% in 11 cases of traumatic dislocation and 78.2±4.6% in 148 casesof control group. 2. There was singnificant difference in G/H ratio between recurrent dislocation and traumaticdislocation (P>0.05) 3. There was significant difference in G/H ratio between recurrent dislocation and controlgroup.(p<0.01) 4. There was singnificant difference in G/H ratio between traumatic dislocation and control group.(p<0.05). Therefore, small glenoid compared with humeral head(low G/H ratio) was meaningful as one of causativefactors in shoulder dislocation.