Ganoderma lucidum is a famous medicinal mushroom that has been widely used in clinical practice and as a dietary supplementa. The triterpenoid ganoderic acids are the main constituents of G. lucidum. To determine the pharmacokinetic characteristics of ganoderic acids, we developed and validated a sensitive and selective liquid chromatography-tandem mass spectrometry method to determine simultaneously the concentration of 4 representative ganoderic acids in rat plasma after oral administration of the extract from G. lucidum. Because of the similarity of their chemical structures, the 4 components exhibited similar pharmacokinetic behaviors in some aspects. However, some of the pharmacokinetic parameters and the reabsorption peaks in the plasma concentration-time curves of ganoderic acids B and E after oral administration of the extract were different from those of ganoderic acids D and A because of the metabolic transformation among the ganoderic acids. These results increase our knowledge about the use of G. lucidum.