An adjustable and retractable needle assembly (10) comprises a deformable hollow needle (12) and a two-part needle housing (14) having a front spigot component (16) and a rear barrel or shield component (18) which are rotatably mounted to one another. The spigot component (16) includes a laterally offset spigot (26) having a guide passage (28) defined therein through which the needle (12) is able to slide. A capstan arrangement (33) extends from the front end of the barrel, and includes a take-up spool (34), with an annular gap (36) being defined between the inner surface (38) of the skirt (20) and the outer surface of the spool (34). The needle (12) is deformed laterally off the axis (30) of the guide passage (28) about a curved interface (48). Counter-clockwise rotation of the barrel (18) relative to the offset spigot causes the needle progressively to wrap around the outer surface of the spool (34) within the gap (36) until the sharp end of the needle is completely retracted into a safe position within the guide aperture (28).
