The paper deals with the calculation of molar refraction ( ) and polarizability ( ) of antibiotic drug ciprofloxacin hydrochloride ( = 0.001-0.029 mol⋅dm −3 ) solutions in ethanol-water mixtures of different compositions (30, 50, and 70% v/v) from measured density ( ) and refractive index ( ) at 30 ∘ C. The effect of drug concentration and composition of ethanol-water mixtures on density and optical properties of drug solutions has been described.