Abstract: A filter with a planar filter insert which includes a device for the deflection of the fluid entering for filtration. Filters of this kind are particularly useful as air filters for the intake air of an internal combustion engine. The device for deflection onto the filter insert 12 is preferably realized by the cross-sectional profile of the inlet chamber 21a. As the hatched plane 26 in FIG. 2 shows, the profile has a curved portion a which leads to a deflection of the flow from an inlet 23 toward the filter insert. In comparison with wedge-shaped inlet chambers, a low pressure region on the filter element near the inlet, which would lead to an unequal distribution of filtrate on the filter element, can be prevented. In this way an optimum useful life of the filter element can be achieved, which is beneficial to the economics of the filtering operation.