Red yeast rice(RYR) also known asMonascus purpureushas been used in China and neighboring Asian countries as food and medicine. RYR is widely known for its antihyperlipidemic effect via inhibiting 3-hydroxy-3-methylglutarylcoenzyme A(HMG-CoA) reductase and thus the catalytic conversion of HMG-CoA to mevalonate, which is a precursor of cholesterol.Monacolins, especially monacolin K, are thesecondary metabolitesresponsible for the lipid lowering activity of RYR extract. Nonetheless, the RYR products are not free of adverse effects. As HMG-CoA reductase inhibitors the RYR extract interferes with the biosynthesis of CoQ10 and causesmyocardial infarction. On the other hand, the statins are metabolized byCYP450enzymes and so do RYR products, hence taking these products withCYP450enzyme inhibitors worsen the risk of adverse effects. In this book chapter, we highlighted the sources, bioavailability, health effects and possible interaction with drugs, foods and other supplements ofMonascus purpureus.Red yeast rice(RYR) also known asMonascus purpureushas been used in China and neighboring Asian countries as food and medicine. RYR is widely known for its antihyperlipidemic effect via inhibiting 3-hydroxy-3-methylglutarylcoenzyme A(HMG-CoA) reductase and thus the catalytic conversion of HMG-CoA to mevalonate, which is a precursor of cholesterol.Monacolins, especially monacolin K, are thesecondary metabolitesresponsible for the lipid lowering activity of RYR extract. Nonetheless, the RYR products are not free of adverse effects. As HMG-CoA reductase inhibitors the RYR extract interferes with the biosynthesis of CoQ10 and causesmyocardial infarction. On the other hand, the statins are metabolized byCYP450enzymes and so do RYR products, hence taking these products withCYP450enzyme inhibitors worsen the risk of adverse effects. In this book chapter, we highlighted the sources, bioavailability, health effects and possible interaction with drugs, foods and other supplements ofMonascus purpureus.