Abstract: Apparatus for injection moulding thermoplastic material is disclosed wherein a heavy-duty sprue bush is heated along a substantial portion of its length to keep the thermoplastic material from solidifying during interruptions in the moulding cycle. The apparatus provides for minimal contact between the heated sprue bush and the moulding die to prevent heat transfer between them. This is achieved by maintaining an air gap between the bush and the die except at points where the thermoplastic material passes into the moulding cavity. Sprue runners oriented generally parallel to the mould joint line are aligned with cavity injection openings which are similarly oriented. These injection openings pass through a thin wall of the mould that extends generally perpendicularly to the joint line such that when the moulds are open, the sprue is cleanly severed from the moulded article.