The pump is of an axial flow rotary pump, suitable for implantation into the human heart or vascular system, and comprises an elongate tubular casing (1,2) defining an inlet (4) for blood, an outlet (5) for blood longitudinally spaced from the inlet, and a primary substantially axial blood flow path (6) along the interior of the casing from the inlet to the outlet, the casing including an electric motor stator (7). There is an elongate rotatable element (3) arranged to fit within the casing with spacing between an outer surface of the rotatable element and an inner surface of the casing. The tubular rotatable element comprises an electric motor rotor portion (10) arranged to be driven by the electric motor stator and a rotary impeller (11) for impelling blood along the blood flow path. The casing is formed as an upstream tubular member (2) having an open front end, and a downstream tubular member (1) having open front and rear ends, the upstream tubular member including the stator, and the downstream tubular member, which encircles the impeller, having a rear end fitted to the upstream tubular member in fluid tight manner.
