A catheter and catheter assembly are disclosed comprising a urinary catheter comprising an insertion end, a rearward end, and a one way check valve arrangement. The check valve arrangement comprises a tubular part of a flexible material, connected to the rearward end of the catheter and extending past the rearward end in a direction opposite to the insertion end, thereby substantially limiting the flow through the catheter to a single direction from the insertion end to the rearward end. Hereby, a very effective anti-reflux function is achieved, and at the same time the construction is relatively simple and inexpensive, and does not require any essential modifications of the other parts of the urinary catheter.