The study was to detemine the effect concentration of lidocaine Hcl $2\%$ iontophoresis for duration of local anesthesia. Emla $5\%$(lidocaine + prilocaine) cream is an oil-in water emulsion system in which the oil phase consists of a cutectic mixture of the base farms of lidocaine and prilocaine in the ratio 1:1. Forty college student between the age of $20.57pm1.94$, weight of $58.50pm9.17Kg$, height $166.87pm8.98 Cm$ were in this study. The results was as follows. 1. Lidocaine Hcl $2\%$ iontophoresis local anesthesia time is $7.15pm2.86$ minutes. 2. Emla $5\%$ cream application to local anesthesia time is $57.32pm40.26$ minutes.