Disclosed are catheter assemblies and methods for insertion of a catheter into a vessel. The assemblies include a resilient valve (40) in the hub of the catheter that can be opened by pressure from a male luer fitting. The methods include piercing a vessel with the needle and catheter of the assembly, retraction of the needle component thus closing the resilient valve. Finally the catheter can be accessed by applying a male luer fitting to the catheter hub and a shoulder of the resilient valve. The valve has a tapered distal surface (42) and a proximal surface (44). The proximal surface has a first recess (45) and a second recess (46) defining a shoulder (48) between. The male luer fitting is inserted into the valve until it contacts shoulder (48) causing the valve flaps (51) to open by the pressure of inserting the luer fitting.
