This study was conducted to analyze metal concentration changes following processing steps for crude, remnant after boiling, and decoction of Korea herbal drugs. We measured meta.! concentration from 20 random patients who visited Oriental medical clinics for treatment of several diseases through normal action. The results obtained were as below: First, in the study to acknowledge quality control between Korean Lab and Harvard Lab in the US, 20 equal herbal samples resulted in the same values, so we confirmed the precision of measurement results from both labs. Second, hazardous metal mean concentration in crude, remnant after boiling, and decoction of herbal drugs were $32.5{mu extrm{g}}/22.1{mu extrm{g}}/8.8{mu extrm{g}}$ for As, $0.0{mu extrm{g}}/0.0{mu extrm{g}}/0.0{mu extrm{g}}$ for Cd, $1.0{mu extrm{g}}/0.0{mu extrm{g}}/0.0{mu extrm{g}}$ for Hg and $5416.3{mu extrm{g}}/3639.6{mu extrm{g}}/1002.6{mu extrm{g}}$ for Pb, respectively. These metal concentrations decreased 72.9-100.0% compared to crude status. The same trend was also visible in the other essential elements. From reviewing these results, we could carefully conclude that decoction had the least amount of metal concentration and is the optimal way to intake herbal drugs.