Twist, a transcription factor of the basic helix-loop-helix class, has been suggested to have oncogenic properties. We reported Twist expression was regulated by Wnt/beta-catenin signaling and that both Wnt-1 and Twist could contribute to mammary tumorigenesis. The aim of this study was to demonstrate the expression of Twist, Wnt-1 and Wnt-2 in human breast cancer tissue. We examined the expression in patients with breast cancer by RT-PCR and immunohistochemistry. RT-PCR of twenty-three pairs of cancer and normal breast tissue revealed that Twist was up-regulated in 69.6% (16/23) of the cancer lesions and 21.7% (5/23) of the normal breast tissues. Wnt-2 was up-regulated in all of the cancer lesions and 13.0% (3/23) of the normal breast tissues, whereas Wnt-1 was expressed in both the cancer and normal breast tissues of the five cases examined. Immunohistochemical analyses revealed that Twist was positively expressed in 52.2% (12/23) of the cancer lesions and 34.8% (8/23) of the normal breast tissues. Twist and Wnt-2 are highly expressed in breast cancer tissue, suggesting that both molecules could play important roles in mammary carcinogenesis.