Exposure to the highly pathogenic H1N1 influenza A viruses is responsible for hundred of frightened deaths in Taiwan this year and the considerable global pandemic threat. Nowadays, medicines such as Tamiflu and Relenza have proven effective in subduing flu symptoms and preventing transmission, but mutation of influenza virus is much more quickly today than they was before. Over time, we have ;en warning signals that drug-resistant influenza viruses cause illness and severe pandemics, disabling our defenses against this pathogen. The increasing drug-resistance to the existing drugs has made a priority fcfor tne need to develop more potent antiviral agents. Among many potential targets, neuraminidase (NA) appears to be an effective target for drug development. According to the X-ray crystal structure of the NA active site, developing NA inhibitors against the drug-resistant virus is feasible. Besides, several flavonoids have been reported that they had anti-influenza virus activity by inhibiting NA activities. Until now, a series of anti-influenza agents have been synthesized by human influenza viruses was examined on the basis of the maximum non-toxic concentration of the test compounds. Some of our products showed potent activity, in vitro, against H1N1 viruses. Further investigations on the mechanisms of action are inprogress.