A technique for direct measurement of the differential diffusion coefficients in a ternary system of water, sugar, and a dilute organic species is described. The individual sugars were d-fructose, d-glucose, and sucrose; and ethyl alcohol, ethyl acetate, n-butyl acetate, and n-hexanal individually constituted the dilute organic species. The four ternary diffusivities were obtained over a range of sugar concentrations by the use of horizontal diaphragm cells, a differential interferometer, a flame-ionization gas-liquid chromatograph and postulation of the validity of the Onsager reciprocal relations. The equilibrium partial pressures of the dilute organic species over these solutions have also been measured, using a vapor head space chromatographic technique.