The changes of the plasma zinc, copper and erythrocyte glutathione peroxidase (GSH-Px) were measured by atomic absorption spectrometry and DTNB color development, in 31 patients suffering from coronary heart disease with angina Pectoris before and after taking Kuo-Guan granule one month. The results showed the plasma zinc was 16.83 +/- 2.60 mumol/L, copper 14.17 +/- 2.99 mumol/L, and erythrocyte GSH-Px 0.75 +/- 0.12 Eu/Hbmg/min in the normal control group. In patients with angina Pectoris, the plasma zinc was 14.39 +/- 4.44 mumol/L, copper 17.47 +/- 4.42 mumol/L, and erythrocyte GSH-Px 0.49 +/- 0.075 Eu/Hbmg/min before treatment; the plasma zinc was 20.17 +/- 3.97 mumol/L, copper 15.74 +/- 3.15 mumol/L, and erythrocyte GSH-Px 0.72 +/- 0.10 Eu/Hbmg/min after treatment. These results indicate that the plasma zinc and erythrocyte GSH-Px were lower and copper was higher in the patients than the normal control group before treatment (P less than 0.01), the plasma zinc and erythrocyte GSH-Px were increased and copper was decreased after treatment (P less than 0.01). These suggest that therapeutic mechanism of Kuo-Guan granule to coronary heart disease with angina Pectoris may be related to it's regulation on trace elements disturbance in body.