This graduate textbook is concerned with both the formulation and the solution of radiation heat transfer problems in enclosures. The book is essentially self-contained and includes a brief historical survey. The foundations are carefully discussed from the point of view of the exact mathematical basis of boundary value problems and their variational solutions as well as of the physical foundations. The computational methods developed by the authors are used in engineering applications. The combinaton of exact mathematical modelling with numerical skills makes this a unique textbook