An arrangement for introducing a liquid medium, e.g. urea, into exhaust gases from a combustion engine, which arrangement comprises: - a line intended to have exhaust gases flowing through it, - an injection chamber which has an upstream end and a downstream end, is bounded in radial directions by a tubular wall and has at its upstream end an inlet for receiving exhaust gases, - an injection means for injecting the liquid medium into the injection chamber, - a mixing duct which forms part of the line and is situated downstream of the injection chamber, which chamber has at its downstream end an outlet for delivering exhaust gases to the mixing duct, and - a bypass duct which is situated in the line upstream of the mixing duct and has an outlet via it is connected to the mixing duct, such that the inlet of the injection chamber is adapted to diverting a portion of the exhaust gases flowing through the line to cause these diverted exhaust gases to enter the injection chamber and thereafter the mixing duct via the inlet of the injection chamber, while the bypass duct is adapted to leading another portion of the exhaust gases flowing through the line into the mixing duct in order to be mixed there with said diverted exhaust gases, characterised - in that the injection chamber has at its downstream end an endwall by which it is demarcated from the mixing duct, - that the side of the endwall which faces in towards the injection chamber is of convex shape, - that the outlet of the injection chamber is situated at the periphery of the endwall, - that the outlet of the bypass duct is situated close to the outlet of the injection chamber so that the exhaust gases which flow into the mixing duct via the outlet of the injection chamber will collide with the exhaust gases which flow into the mixing duct via the outlet of the bypass duct and - that the outlet of the injection chamber is situated between said tubular wall and the periphery of said endwall. - a line intended to have exhaust gases flowing through it, - an injection chamber which has an upstream end and a downstream end, is bounded in radial directions by a tubular wall and has at its upstream end an inlet for receiving exhaust gases, - an injection means for injecting the liquid medium into the injection chamber, - a mixing duct which forms part of the line and is situated downstream of the injection chamber, which chamber has at its downstream end an outlet for delivering exhaust gases to the mixing duct, and - a bypass duct which is situated in the line upstream of the mixing duct and has an outlet via it is connected to the mixing duct, - in that the injection chamber has at its downstream end an endwall by which it is demarcated from the mixing duct, - that the side of the endwall which faces in towards the injection chamber is of convex shape, - that the outlet of the injection chamber is situated at the periphery of the endwall, - that the outlet of the bypass duct is situated close to the outlet of the injection chamber so that the exhaust gases which flow into the mixing duct via the outlet of the injection chamber will collide with the exhaust gases which flow into the mixing duct via the outlet of the bypass duct and - that the outlet of the injection chamber is situated between said tubular wall and the periphery of said endwall.