Objective: To detect the change of p38 protein expression and investigate the relationship of p38 and lymph nodes metastasis in human breast carcinomas. Methods: Sixty breast cancer cases were checked by S-P immunohistochemistry technique and 30 breast cancer cases were examined by Western Blot. Results: Immunohistochemical results showed that p38protein was observed in breast cancer and normal cytoplasm. P-p38 was positive in nucleus in breast cancer. P38 protein expressed positively in 29 out of 38 patients who had lymph nodes metastasis (positive rate 76.3%) and in 9 out of 22 patients who had no lymph nodes metastasis (positive rate 40.9%). There was a significant difference between these two groups (P＜0.01). The positive rate of p-p38 in patients who had lymph nodes metastasis was 68.4%, and the positive rate in patients who had no metastasis was 36.4%, and there was a significant difference between these two groups (P＜0.05). The result of western blot showed that the protein contents of p38 and p-p38 in patients with metastasis was higher than those in patients without metastasis (P＜0.05). P38 and p-p38 protein expressions had relation with clinical pathological grades in breast cancer, higher in grade Ⅲ than in grade Ⅰ, Ⅱ (P＜0.05), while had no relation with patients age and tumor size (P＞0.05).Conclusion: p38 and p-p38 protein expressions had relationship with lymph nodes metastasis and the levels of p38 and p-p38protein expression in groups with lymph nodes metastasis were higher than in groups without lymph nodes metastasis. P38and p-p38 protein expressions had relationship with clinical grades and had no relationship with patients age and tumor size.