A discussion of an effective computational solution for a classical problem of long standing in the theory of transport processes: the determination of the internal intensity function in a finite, homogeneous, isotropically scattering slab which is illuminated by uniform parallel rays of radiation. The authors employ an imbedding technique to solve the problem. They demonstrate how to compute the source function, characterized as the solution of a system of ordinary differential equations with a complete set of initial conditions. The X and Y functions of Chandrasekhar play a key role. 17 pp. Bibliog.