BACKGROUND: RET/PTC rearrangement and mutations of BRAF and ras are well-known oncogenes involved in the pathogenesis of papillary thyroid carcinoma (PTC). The prevalence of RET/PTC rearrangement and BRAF mutations were 0~13% and 66~83% in Korean patients with PTC, respectively. We evaluated the prevalence of ras mutations in surgical specimens of PTC, and we compared them with the patients' clinical features. SUBJECTS AND METHODS: We included the surgical specimens of 49 PTCs and a few follicular thyroid carcinomas (FTCs) and follicular adenomas (FAs) as positive controls. Polymerase chain reaction, single strand conformation polymorphism and direct sequence analysis were consecutively performed to detect ras mutations. RESULTS: No mutations of the ras oncogenes were detected in 49 PTCs. However, heterozygous mutations of the ras oncogenes were found in a FTC and FA as positive controls, respectively. CONCLUSION: These findings suggested that ras mutation is not or rarely related to the tumorigenesis of PTCs in Koreans. Therefore, BRAF mutations and RET/PTC rearrangement, rather than ras mutation, might contribute the development of PTC in Koreans.