Abstract: The present invention concerns a method and equipment for distribution of two fluids into and out of the channels in a multi-channel monolithic structure (monolith) where the channel openings are spread over the entire cross-sectional area of said structure. Said equipment consists of a manifold head, a monolith unit or a monolith stack, or a row of said units or stacks or a monolith block. Furthermore, the present invention concerns a method and a reactor for mass and/or heat transfer between two fluids where said fluids are distributed through one or more of said manifold heads and units or stack or row of units or stacks or blocks.