The antioxidant activity of the methanolic extracts of 4 plants from genus Helichrysum Mill. (Asteraceae) [H. arenarium (L.) Moench subsp. erzincanicum Davis & Kupicha, H. arenarium (L.) Moench subsp. rubicundum (C.Koch.) Davis & Kupicha, H. armenium DC. subsp. araxinum (Kirp.) Takht., and H. plicatum DC. subsp. pseudoplicatum (Nab.) Davis & Kupicha] was investigated with 2 complementary test systems, DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging and phosphomolybdenum assay. H. plicatum subsp. pseudoplicatum showed the highest level of total antioxidant activity (161.79 +/- 0.3 mg ascorbic acid equivalent/g extract) in the phosphomolybdenum assay. H. arenarium subsp. erzincanicum showed the highest level of free radical scavenging activity, with an IC50 value of 23.03 mu g/mL. The total phenolic contents of the extracts ranged from 71.81 to 144.50 mg gallic acid/g dry extract. Chlorogenic acid, apigenin-7-glucoside, and apigenin were found by HPLC analysis to be the main components in the extracts. Antimicrobial activity was investigated with the agar diffusion method. The methanolic extracts had antibacterial activity against Aeromonas hydrophila, Bacillus brevis, B. cereus, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Staphylococcus aureus ATCC 29213. However, no activity was found against Escherichia coli, Morganella morganii, Mycobacterium smegmatis, Proteus mirabilis, Yersinia enterocolitica, or Saccharomyces cerevisiae.