Purpose: To determine the incidence of anatomic variations of the hook of hamate and to evaluate its association with the development of carpal tunnel syndrome (CTS) in Korean patients. Materials and Methods: Carpal tunnel views of 916 hands (458 patients) that received out-patient treatment for tingling hands, from March 2008 to November 2009. The sex distribution was 69 men and 389 women and the average age was 52.7 years old. The frequency of appearance of variations of the hamate and the ratio of each variation were identified. In addition, patients with variant hooks of hamate with CTS were compared to patients with variant hooks of hamate who had no evidence of CTS. The counting variant age and the correlation of the variant of the hooks of hamate and the occurrence of CTS were analyzed. Results: Variations of the hook of hamate were found in 48 of 916 hands. The ratio of width to height averaged 0.97 with a standard deviation of 0.32. Twenty-five right hands and twenty-three left hands were studied. Four men and forty four women were found with variations but there was no statistical significance to this finding. CTS was diagnosed in 42 of 48 patients. This group accounted for 6.1% of all patients diagnosed with CTS. Out of 42 patient cases 9 were bipartite hook cases, 27 were hypo plastic cases, and 6 were aplastic cases. Six cases, which made up 2.5% of the patients, were not diagnosed with CTS. These cases consisted of two bipartite cases, three hypo plastic cases, and one aplastic case. When the two groups were analyzed by Chi-square test & Fisher’s exact test, there was a higher incidence of variation with the group that was diagnosed with CTS than with the others (P=0.0282). Conclusion: The variations of the hook of hamate are found in 5.2% of the patients in this study. This variation appears to be one of the causal factors of CTS.