In reactor kinetics problems where it is desirable to take the space dependence of reactor flux into account, the time dependent diffusion equation must be solved. The solution of this equation on an analog computer requires a large amount of equipment. If the equation is written the form, where the volume integral of the divergence of neutron current has been replaced by the surface integral of the current, then a large reduction in the number of mesh points and consequently in the amount of equipment is possible. An example is given and compared with the flux distribution computed on a digital machine.