To search for bioactive compounds from plant resources, 80% methanol extracts of 46 species of weeds were screened for their activities of antimicrobial, antioxidative, antiblebing, antitumor and herbicidal. Among extracts tested, some showed activities at the concentration of 50 to 100 ㎍/㎖. Phryma leptostachya var. asiatica, Aster ageratoides, Centipede minima, Cirsium pendulum, Lythrum anceps showed antibacterial activity. Penthorum chinense, Lindernia procumbens, Aster ageratoides, Dianthus superbus var. longicalycinus showed antiblebing activity. Phyma leptostachya var. asiatica, Juncus effusus var. decipiens. Lindernia procumbens. Aster ageratoides, Dianthus superbus var. longicalycinus, Viscum album var. coloratum showed antitumor activity. Juncus effusus var. decipiens, Hypericum asoyron, Juncus papillosus, Inula britannicar var. chinensis, Scirpus wichurae, Hypericum laxum showed antioxidant activity.