The paper is concerned with measurements of the surface tension of aqueous binary solutions at low temperatures. The effects of both temperature and concentration on the surface tension of CaCl2, NaCiO(3), and propylene glycol have been investigated. A differential capillary-rise method was employed for the measurements. The results showed that the surface tension of CaCl2 and NaClO3 increases monotonically as the concentration of the solution increases, while for the propylene glycol solution the surface tension decreases with increasing concentration. The surface tension of the testing liquids was found to be an almost-linear function of temperature from 20 degrees C to just above the freezing temperature. Equations for the surface tension of the three aqueous binary solutions as a Function of temperature and concentration are presented.