Abstract: FIG. 2 shows a lancet device for performing a pricking operation. A barrel (36) is closed at one end by a finger guard plate (43) having a centrally positioned hole (42). Prior to use, the hole (42) is closed by a centrally disposed axially protruding spigot (54) found on the inside of a cap 40. In use, the cap is removed and the spigot (54) is inserted into the other end of the barrel (36) to bear against a shank 44 of a needle assembly 16 is secured to the periphery of a hole (46) in an end plate (48). A finger to be pricked is placed against the finger guard plate (43) and a thumb is placed over the cap (4) which is now located over the other end of the barrel from that shown in the drawing.Pressure between the thumb and finger causes the spigot (54) to break the attachment between the shank of the needle and the periphery of the hole (46) to allow the needle assembly to be projected through the barrel (36) under the force exerted by a compressed spring (16).