The invention relates to a heat exchanger (1), in particular an air-cooled air cooler consisting of a block (2) with first (7) and second (9) flow channels, arranged in a cross-flow configuration, for a first gaseous medium that is to be cooled and a second cooling gaseous medium. According to the invention, the first flow channels (7) are connected on the inlet and outlet side to collection contairers (4) mounted on the block (2) and fins (10) are located in the second flow channels (9).