Neuraminidase (NA) is one of the two major surface antigens of influenza virus. It plays an indispensable role in the release and spread of progeny virus particles during infection. NA inhibitors reduce virus infection in animals. To improve the clinical efficacy of NA inhibitors, we have begun the design of non-carbohydrate inhibitors based on the active site structure of NA. The approach is an iterative process of ligand modeling and electrostatic calculations followed by chemical synthesis of compounds, biological testing, and NA-inhibitor complex structure determination by X-ray crystallography. A strategy has been developed to calculate Ki for newly designed inhibitors. The calculations using the DelPhi program were performed for carbohydrate inhibitors and three preliminary benzoic acid inhibitors of neuraminidase (BANA) that have been synthesized and shown to bind to the active site of NA in the crystal structure. The calculated Kis of these inhibitors have an enlightening agreement with their in vitro biological activities. This demonstrates that the calculations produce informative results on the affinity of modeled inhibitors. GRID maps were also calculated and several pockets were identified for accepting possible new ligands. The calculated Kis for newly designed ligands suggest that these potential compounds will have high inhibitory activities.