We analyzed germline mutations of the BRCAl gene in 29 Korean breast cancer patients, which included ¨c 10 breast cancer patients with family history of breast or ovarian cancer, ¨e 7 early onset breast cancer patients without family history of breast or ovarian cancer(1ess than 40 years old at diagnosis) and ¨e 12 breast cancer patients without family history of breast or ovarian cancer(more than 40 years old at diagnosis), and 1 hereditary ovarian cancer patient. One nonsense mutation at codon 1815 encoding a truncated protein was detected in a breast cancer patient with family history of ovarian cancer. One missense mutation at codon 1630 was detected in a group of breast cancer patients without family history(more than 40 years old at diagnosis), but still not determined whether it was polymorphism or not. Three polymorphisms were detected, which included 2 cases of silent mutation and a case of missense mutation. In early onset breast cancer group and a familial ovarian cancer patient, there was no detected mutation. We confirmed a germline BRCAl gene mutation in one Korean patient of hereditary breast-ovarian cancer family.