The occurrence of triterpene pentacyclic acids in plants is extensive, but little is known about their availability in commercial extracts. A simple GC-MS method for the simultaneous determination of betulinic, corosolic, maslinic, oleanolic and ursolic acids was developed and applied to 38 different commercial plant extracts sold as ingredients for dietary supplements. A suitable protocol was set up to perform routine control of a diverse array of samples with different botanical, chemical and physical characteristics. Remarkable quantities of corosolic acid were found in dried extracts from aerial parts of Lagerstroemia speciosa and Ortosiphon stamineus (14233 and 1132 mg/kg, respectively), while oleanolic acid was abundant in O. stamineus and Crataegus monogyna flowers (2774 and 2339 mg/kg); ursolic was identified in O. stamineus, C. monogyna, L. speciosa and Arctostaphylos uva-ursi leaves (7773, 4165, 2108 and 1034 mg/kg). Only L. speciosa was rich in maslinic acid (4958 mg/kg), while minor amounts of betulinic acid (257 and 80 mg/kg) were detected in L. speciosa and C. monogyna extracts. Lower quantities of triterpenic acids were identified in dried extracts of Harpagophyton procumbens root, propolis, Punica granatum root, Styrax benzoin, Vaccinium myrtillus fruits and Vitis vinifera seeds. Decoctions and fluid extracts lacked or contained very low amounts of triterpenic acids. Results are discussed in terms of quality and safety of these ingredients.