AbstractThis paper describes four benchmark problems to validate magnetohydrodynamic and heat transfer computer codes. The problems include rectangular duct geometry with uniform and non-uniform magnetic fields, with and without surface heat flux, and various rectangular cross-sections. Two of the problems are based on experiments. Participants in this benchmarking activity come from three countries: Russia, USA and Japan. The solution methods to the problems are described. Results from the different computer codes are presented and compared.