OBJECTIVE: To evaluate the efficacy and safety of aromatase inhibitors in the treatment of advanced breast cancer. METHODS: A total of 52 patients with advanced breast cancer with observable lesions were observed from 2003.6 to 2006.9, treated with aromatase inhibitors for at least 24 weeks, among which 11 cases were treated for less than 24 weeks due to rapid disease progression; age range was 37-75 years, mean age 58 years, among which 6 of 8 premenopausal patients had ovariectomy and 2 cases were treated with concomitant application of Norelide to suppress ovarian function. The aromatase inhibitors used by the patients were exemestane in 36 cases, anastrozole in 13 cases and letrozole in 3 cases; the primary endpoints of the study were objective tumor response rate (ORR: CR+PR), clinical benefit rate (CBRCR+PR+SD>24 weeks), time to tumor progression (TTP), time to tumor treatment failure (TTF), safety and toxic side effects. Results: 6 cases of CR (11.5%), 1 case maintained more than 132w, 1 case had 96w, another 4 cases >60w; 19 cases of PR (36.5%), the longest time to maintain PR was 96w, the rest were >32w; SD>24w in 16 patients 30.8%, PD plus SD <24 weeks in 11 cases (21.2%); ORR was 48%, CBR was 78.8% and mean TTP time 78.87 weeks (95% CI 61.13-96.61%); despite the fact that patients without ORR took other treatments including chemotherapy, radiotherapy and another class of aromatase inhibitors after disease progression, survival time was still significantly different between patients who achieved ORR and those without ORR using Kaplan-Meier survival curves, p= 0.047; drug-related side effects included rash, flushing, sweating, and small joint pain, including 2 cases of heart failure that were indeterminate with the treatment drug and improved with symptomatic treatment. Conclusion: Aromatase inhibitors are 78.8% effective in the treatment of advanced breast cancer as a single agent , with long-term survival in patients who achieve CR or PR, and side effects are easily tolerated.