The use of a novel macrocyclic molecule, cucurbit[7] uril (CB[7]), as an additive in capillary electrophoresis (CE) for the separation of several neutral nitrobenzenes is reported. Disodium hydrogen phosphate-hydrochloric acid was used as the buffer solvent with the UV detection at 254 nm. During the running process, CB [7] bore positive charge under the studied pH range (pH 2 - 6.5) and was adsorbed onto the inner wall of fused silica capillary, leading to a reversal of the electroosmotic flow (EOF). The effects of buffer pH and CB [7] concentration on the EOF behavior were investigated. The influences of the CB [7] concentration on electrophoretic behaviors of nitrobenzenes were also studied, and it was found that the selectivity increased with CB[7] concentration. The results showed that CB [7] provided good selectivity for nitrobenzenes and successful separation was obtained under optimum condition (10 mmol/L Na2HPO4 (pH 2.47, adjusted by HCl)-methanol (90 : 10, v/v), containing 5 mmol/L CB[7]). Possible explanation is also proposed.