We investigated the effects of dietary supplements on atria isolated from male Wistar rats. The examined supplements, which are increasingly used in Japan, those were Ginkgo biloba extract (GBE), catechins, isoflavones, sodium iron chlorophyllin and sodium copper chlorophyllin. GBE at 100—1000 µg/ml significantly increased the beat rate and the contractile force. Catechins at 1—100 µg/ml significantly potentiated the contractile force but did not effect the beat rates. However, isoflavones, sodium iron and sodium copper chlorophyllins did not change the contractile force or the beat rates. To identify the active ingredient of GBE, ginkgolide B, quercetin and amentoflavone on the atria were tested. Ginkgolide B weakened the contractile force. Quercetin potentiated the contractile force at only 30 µg/ml. Amentoflavone significantly increased the beat rate. From these findings, amentoflavone and quercetin were considered to be the principal ingredients of GBE producing the positive chronotropic and inotropic actions, respectively. In the case of catechins, (−)-epigallocatechin gallate (EGCg), one of the principal ingredients, produced inotropic actions. These findings suggest that there are some dietary supplements which affect cardiac function, such GBE and catechins.