A theory of light scattering from a simple AB reacting fluid in which molecular anisotropy has been neglected is presented. The theory is a molecular-statistical one based on Mori's linear response formalism. The time-dependent correlation functions are associated with transport coefficients and the zero time correlation functions are associated with thermodynamic derivatives. The effects of the reaction are observed from both density and concentration fluctuations as well as from cross correlations between density and concentration fluctuations.