Cratoegus sp., also known as "hawthorn", is one of the most prescribed herbal drugs and approved to be used against congestive heart failure. The extract is required to be standardized according to its flavonoid (vitexine-2"-O-rhamnoside and hyperoside) and oligomeric procyaniclin content by the European Pharmacopoeia (EP). In this study, the leaves and berries of three Crataegus species including C. aronio var. aronia, C. monogyna ssp. monogyno (from two different localities) as well as C. pseucloheterophylla growing in Turkey were evaluated for their vitexine-2"-O-rhamnoside and hyperoside content by reversed-phase HPLC as well as their total procyaniclin amount by a spectrophotometric method. In addition, antibacterial, antifungal, and antiviral activities of the extracts were also determined. Our results indicated that C. monogyna ssp. monogyno samples of both localities met the criteria required by the EP for their total flavonoid amount (2.49 and 2.86%) and total proanthocyanidin content (1.56 and 2.22%). According to data we obtained, the extracts have been verified to be highly effective against Candida albicons and Herpes simplex virus.