A needle assembly of a metal shaft (10, 10&prime) and an outer plastics sleeve (12) is made by extruding the sleeve onto the outside of the shaft. The sleeve contains gas bubbles (13), preferably with a size in the range 5 &mu to 10 &mu, to increase the ultrasound visibility of the assembly. A sharp, penetrating tip (18) may be formed on the shaft either before or after the sleeve is extruded on the shaft. The metal shaft (10) may be supplied to the extruder 1 to 5 in a continuous length and cut to the size of the needle assemblies after extrusion of the sleeve (12). Alternatively, pre-cut lengths of metal shafts (10&prime) could be supplied to the extruder 1&prime to 5&prime, the sleeve being cut between the shafts after extrusion.
