A self-cleaning filter device comprises a fluidic oscillator having a pair of passages through which fluid is directed alternately, and filter elements which fluid can flow from said passages to an auxiliary outlet. A main outlet communicates with the passages in such a way that the filter elements do not impede fluid flow to the main outlet. Between each passage and the main outlet is a device which provides a higher impedance to flow from the main outlet to the passages than to flow in the opposite direction, and assists the self-cleaning action of the filter elements by increase the difference between the fluid pressures in the passages.