The purpose of the current study was to investigate the possible antimicrobial and anticancer properties of the aquatic moss Fontinalis antipyretica Hedw. (Fontinalaceae). We first obtained 8 different extracts (methanol; chloroform; acetone; ethyl acetate A, B, C, and D) by two different extraction processes. The antimicrobial activity of these extracts was then assessed by using the well diffusion method against 8 bacterial and 7 fungal strains. The results of antimicrobial studies showed that extracts of chloroform, acetone, and ethyl acetate A and C were active against almost all the species tested. The most effective extract was C, which was then screened through a preparative TLC (bioautography) for its active components. Spot 4 of extract C exhibited the highest antimicrobial activity against 5 bacterial strains (B. cereus, B. subtilis, E. faecalis, E. acrogenes, and Y. enterocolitica) and 3 fungal strains (A. flavus, F. solani, and F. graminearum), with MIC values of 93.8-375.0 mu g/mL and 187.5-375.0 mu g/mL, respectively. In addition, in vitro toxicity of the active component of extract Cat the concentrations of 0.16, 1.6, 16, 80, and 160 mu g/mL was tested. Depending on dose and time, only 80 and 160 mu g/mL decreased rat glioma (C6) cell viability after 24 or 48 h. The present study suggests the possibility that Fontinalis antipyretica possesses antimicrobial and anticancer agent(s).