Objective To evaluate the efficacy of mydriasis induced by intracameral injection of 1% lidocaine instead of topical mydriatics and postoperative recovery of pupil diameter in phacoemulsification surgery through a prospectively controlled clinical trial. Design Randomized clinical trial. Participants 34 patients (36 eyes) in study group,46 patients (50 eyes) in control group. Methods The study group comprised 34 patients (36 eyes),who were given intracamerally 0.5 ml unpreserved lidocaine 1% without using mydriatic eyedrops preoperatively. 46 patients (50 eyes),pupil dilated with topical mydriatics,Mydrin-p ( Tropicamid,Phenylephrine Eye Drops),were studied for comparison. As for the study group,baseline pupil diameters were recorded before the surgery,and 90 seconds after the injection of 1% lidocaine. As for the control group pupil,diameters were recorded when the surgery began. Pupil diameters at 1h,2h,4h,8h,12h,and 24h postoperatively were recorded respectively for both groups. Corneal edema and vision recovery were recorded postoperatively. Main outcome measures Pupil diameter. Results The mean baseline pupil size of the study group was 2.0611?0.1016mm,and maximum mean pupil size obtained at 90 seconds after the injection was 6.0972?0.1566mm. At the beginning of the surgery the mean pupil diameter of the control group was 7.6100?0.0799mm which was larger than 6.0972?0.1566mm (P=0.000). 75.0% eyes in the lidocaine group returned to normal size with brisk light reflex,while only 22.0% in the control group did. The time required for return to normal pupil size was significantly different between the two groups (P=0.000). Conclusions Intracameral injection of 1% unpreserved lidocaine can provide adequate pupil dilation and get rapid recovery of pupil size after surgery,though not as large as that of topical mydriatics for phacoemulsification. (Ophthalmol CHN ,2006,15: 205-208)