Specific refractive index increments of three agarose samples in dimethyl sulfoxide and in water were measured at 436, 546 and 633 nm, and at several temperatures. The wavelength and temperature dependences of the increments were determined, simultaneously correlated using the surface repression method, and presented in a form suitable for tabulation. The influence of differences in the structure of agaroses from various algal sources on the specific refractive index increment is discussed.