Abstract: A ball-and-socket joint prosthesis developed for the shoulder has one component in the form of a ball connected through a neck to a stem, a first cup engaged with the ball in a snap fit which is held captive by a first clip connected round the cup, and a second cup releasably engaged around the remainder of the ball. The second cup is slotted from its rim to accommodate the first component neck and so predetermine the relative positions of these parts, and the second cup rim is complementary with that of the first cup to predetermine the relative positions of the cups around the ball. The resultant assembly therefore fixes the relative positions of the one component and first cup to facilitate securement of these parts, while keeping the articular surfaces free of cement, and the second cup is removed after securement to leave a stable captive ball-and-socket joint.