The present invention relates to a method and a toilet arrangement in a house trailer or camper, which toilet arrangement (1) comprises a module unit comprising a floor surface (3) constituting a minor part of the total floor surface of the camper/house trailer, as well as a toilet chair wall (4), and a toilet chair (2) arranged on top of said floor surface (3) and at said toilet chair wall, wherein said toilet chair (2) consists of a combustion toilet with a combustion vessel (32), which is provided with a back (10B) which is secured at the inside of said toilet chair wall (4) and a part (10A) protruding from the back and provided with a flue gas outlet (52), which part extends through an opening (41) in said toilet chair wall (4), as well as that said flue gas outlet (52) is connected to an exhaust pipe (5) ending in a chimney (6) on top of the roof (200) of the camper/house trailer, and in this way a toilet arrangement is provided which is advantageous from an environmental point of view.