Flixweed seeds were collected from suspected winter wheat fields and remote hillside in Shaanxi Province, China, their sensitivities to tribenuron-methyl were evaluated in the greenhouse. Results revealed that biotype S was susceptible to tribenuron, and its GR(50) was 0.23 g a.i. ha(-1), whereas biotypes R1, R2, R3, and R4 were resistant to the tribenuron, and their GR(50) were 161.99, 79.70, 439.80, and 312.30, respectively. Biotypes R1 and R2 showed moderate resistance with resistant indices (RI) of 615.23 and 302.7, respectively. Whereas biotypes R3 and R4 showed high resistance to the herbicide with RI values as high as 1 670.34 and 1 186.10, respectively.