In order to understand molecular interactions between simple amino acid such as glycine and antituberculosis drug isoniazid, the density (r), relative viscosity ( h r) and refractive index (nD) of ternary glycine (0.02-0.34 mol·dm-3) + {aqueous isoniazid (0.02 mol·dm-3)} solutions of were measured at 298.15 K. Apparent molar volumes ( j v ) were calculated from density data and fitted to Massons relation to get partial molar volume (j0 v) of glycine at infinite dilution in aqueous 0.02 mol·dm-3 isoniazid solution. Viscosity data was analyzed by Jones-Dole relation and viscosity B-coefficient for solute-solvent interaction was determined graphically. Refractive index data was used to calculate specific refraction (RD). Interactions between solute and co-solute have been interpreted form partial molar volume of transfer (Dtrj0 v). Measured and derived properties have been interpreted in terms of glycine-water, drug-water and glycine-drug interaction in binary and ternary solutions.