Objective To investigate the changes of serum homocysteine (Hcy) level before and after treatment in patients with colorectal cancer,and provide the reference for clinical therapeutic efficacy and prognosis.Methods Enzymatic circling assay was used to measure the serum Hcy levels in 50 controls and 58 patients with colorectal cancer before and after treatment with a.follow-up of 12 months.The changes of Hcy aud the relationship between Hcy and therapeutic efficacy or prognosis were analyzed.Results Scrum Hcy level in patients with colorectal cancer was significantly higher than that in controls [(16.90±5.35) μmol/L vs (10.23±3.06) μmol/L] (P ＜ 0.01),and it was closely associated with TNM stage.Serum Hcy level in patients of stage Ⅲ-Ⅳ was significantly higher than that of stage Ⅰ-Ⅱ [(18.49±5.13) μmol/L vs (15.20±4.86) μmol/L] (P ＜ 0.05).The Hcy level in patients at the end of treatment was significantly lower than that before treatment [(13.39±4.98) μmol/L vs (16.90±5.35) μmol/L] (P ＜ 0.01),and the Hcy level after the treatment for 3 month was significantly lower than that at the end of treatment [(10.23±3.17) μmol/L] (P ＜ 0.05).The Hcy level in patients with recurrence during 12 months after operation was significantly higher than that without recurrence [(17.18±4.82) μmol/L vs (12.36±3.19) μmol/L] (P ＜ 0.01).Conclusion Serum level of Hcy might be a useful marker for predicting therapeutic efficacy and prognosis in patients with colorectal cancer.