A quantitative theory of the scattering from systems in which a precipitating phase is undergoing diffusion‐controlled growth is worked out by means of a Fourier transform method, and is applied to experimental data on light scattering from phase‐separated glasses. The theory predicts an initial inverse eighth‐power dependence of turbidity on wavelength, a great excess of backward scattering over forward scattering, and under certain conditions a minimum in the plot of intensity against scattering angle, all of which are in agreement with observation.