Effect of norfloxacin and sparfloxacin on the corrosion of zinc in 0.001- 0.005M H2SO4 have been studied. Both compounds inhibit the corrosion of zinc in H2SO4 medium. Their inhibition efficiency is most affected by concentration of H2SO4 and temperature.Agraduation in thermodynamic parameters of adsorption(ïHads, ïGads, and Ea)of norfloxacin and sparfloxacin was observed between H2SO4 concentration range of 0.01- 0.03M and 0.03-0.05M respectively. Although activation energies of norfloxacin and sparfloxacin inhibited corrosion reaction of zincwere positive and greater than activation energy of uninhibited corrosion reaction of zinc, a significant statistical differences (Pï£0.05) was observed between the values of Ea obtained for norfloxacin and sparfloxacin. Corrletaion between the two set of data was also weak. Values of ïHads and ïGads were negative for both inhibitor sand were also found to be significantly difference fromeach other.