A single use retractable syringe (10) has an inner barrel (44) supporting a needle (16) at one end and is slidable within an outer barrel (11). In the packaged condition the inner barrel is in a position relative to the outer barrel such that the needle can be attached to a Luer connection on the inner barrel and projects from a first end (18) of the outer barrel. The inner barrel has first and second latching means (40, 41, 43) adjacent each end, respectively, and the outer barrel has retaining means (48) on the inner wall surface adjacent the second end thereof. When the inner barrel first latching means (40) is engaged with the retaining means the syringe is in position ready for use and after the first full depression of a plunger the inner barrel is released and moves to a position where the second latching means (41, 43) becomes permanently engaged with the retaining means. The needle is then fully enclosed within the outer barrel and the inner barrel projects from the second end (19) of the outer barrel.