The present invention provides apparatus and methods for injection molding polymeric cannulae from liquid polymeric materials. The method includes injecting pressurized liquid polymer into a mold cavity and into an overflow and forming a conduit by forcing pressurized working fluid through the solidifying liquid polymer into the overflow. The invention provides a mold for fluid-assisted injection molding articles from polymeric materials, the mold comprising at least two parts defining a cavity having a conduit portion incorporating a needle portion a channel for liquid polymer ingress a channel for pressurized fluid ingress and an overflow in communication with the conduit portion. The mold may incorporate a plurality of cavities. Preferably the volume of the overflow is equal to or greater than the volume of the conduit portion. Preferably the mold incorporates a separating means for separating the overflow from a cannula portion of an article formed in the mold.
