1. Objectives To compare the contents of heavy metals, residual pesticides and sulfur dioxide before/after decoction. 2. Methods The heavy metal contents before/after decoction were measured by Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES) and mercury analyzer. In order to analyze pesticides in 3 samples we used simultaneous multi-residue analysis of pesticides by GC/ECD, followed by GC/MSD analysis to confirm the identity of the detected pesticide in each sample. In addition, the contents of sulfur dioxide (SO2) were performed by Monier-Williams distillation method. 3. Results 1) The mean values of heavy metal contents (mg/kg) for the samples were as follows: Yuldahanso-tang (before decoction - Pb; 1.85, Cd; 0.148, As; 0.042 and Hg; 0.003, after decoction - Pb; 0.096, Cd; 0.006, As; 0.006 and Hg; 0.002), Chongsimyonja-tang (before decoction - Pb; 1.193, Cd; 0.094, As; 0.084 and Hg; 0.008, after decoction - Pb; 0.053, Cd; 0.007, As; 0.011 and Hg; not detected) and Taeyeumjowee-tang (before decoction - Pb; 0.878, Cd; 0.078, As; 0.302 and Hg; 0.004, after decoction - Pb; 0.079, Cd; 0.005, As; 0.006 and Hg; not dectcted). 2) Contents (mg/kg) of residual pesticides before/after decoction in all samples were not detected. 3) Contents (mg/kg) of sulfur dioxide (SO2) before decoction in Yuldahanso-tang, Chongsimyonja-tang and Taeyeumjowee-tang exhibited 6.1, 37.8, 31.5 and 19.7, respectively. However, contents of sulfur dioxide after decoction in all samples were not detected. 4. Conclusion These results will be used to establish a criterion of heavy metals, residual pesticides and sulfur dioxide.