OBJECTIVE To evaluate the accuracy of endorectal ultrasonography in preoperative staging of rectal carcinoma. METHODS The 319 patients with rectal adenocarcinoma underwent endorectal ultrasonography evaluation from January 2007 to March 2010. There were 175 males and 144 females, and the age of patients were 22-82 year old (median 59 years). According their visiting time, 319 patients were divided into 3 groups (period A: January to December 2007; period B: January to December 2008; and period C: January 2009 to March 2010). All patients underwent endorectal ultrasonography, and the 3 doctors had finished evaluations with 272 cases (Doctor 1, 2, 3 had finished evaluations with 162, 64 and 46 cases respectively). The endorectal ultrasonography staging was compared with the pathology findings based on the surgical specimens in 319 patients who had surgery. RESULTS Overall accuracy in assessing the level of rectal wall invasion was 67%. The accuracy of uT2 and uT3 were 43% and 81% respectively, and the difference was statistically significant (χ(2) = 30.54, P < 0.01), and the accuracy of uT4a was 59%, which was lower than uT3 (81%,χ(2) = 13.77, P < 0.01). Overall accuracy in assessing nodal involvement in the 311 patients treated with radical surgery was 66%. Staging accuracy tends to improve with experience, the accuracy with Doctor 1 in period C(staging accuracy of T and N were 84% and 81% respectively) were higher than period A(staging accuracy of T and N were 55% and 41% respectively) (χ(2) = 6.65 and 13.27, P < 0.01). CONCLUSIONS Transrectal ultrasound for preoperative staging of rectal has higher accuracy with mastered ultrasound doctor.