Objective To investigate the expressions of Snail mRNA and E-cad mRNA in invasive ductal carcinoma and their clinical significance. Methods The expression of Snail mRNA and E-cad mRNA were detected on mammary gland hyperplasia (30cases), intraductal breast carcinoma(30cases) and invasive ductal carcinoma (70cases)by in situ hybridization. Results The positive expression rate of Snail mRNA and E-cad mRNA in mammary gland hyperplasia, intraductal breast carcinoma and invasive ductal carcinoma were 23. 3% ,46. 7% ,81.4% and 96. 7% ,66. 7% ,35.7% ,respectively. There was significant difference among them(P ＜ 0. 01). There was difference between Snail mRNA and E-cad mRNA in the same group(P ＜0. 05). Snail mRNA was not related to age, tumor size or histopathological grade (P ＞0. 05) ,but it was related to lymphatic metastasis (P ＜0. 01). E-cad mRNA was not related to age, tumor size(P ＞0. 05),but it was related to lymphatic metastasis and histopathological grade(P ＜0. 01). There were positive relationship between Snail mRNA and E-cad mRNA(r = -0. 56, P =0. 00). Conclusions The overexpression of Snail mRNA and low expression of E-cad mRNA were involved in the infiltration and metastasis of breast carcinoma, and they were related to lymphatic metastasis. Therefore, the test of the expression of them were valuable in predicting the prognostic and metastasis of breast carcinoma.