A catheter device, comprising a venipuncture needle or stylet whose shank extends through the bore of a catheter or cannula and has a sharpened tip projecting slightly therebeyond in an extended position of the needle to provide an outside-the-needle catheter unit for venipuncture and for insertion of the catheter in a vein in largely conventional manner, and a housing adapted to define an elongate liquid flow chamber. Such housing is connected, liquid-tight, at one end to the catheter and is adapted to protectively house the sharpened tip of the needle following venipuncture. The housing itself is liquid-tight, except for an opening at its other end through which extends tubing for the supply of a venoclysis liquid. The other end of the needle may be provided with a hub formed as a stopper for fitting tightly in a seat formed in the housing immediately in advance of the opening, or may be provided with a hub that is attached to the supply tubing at the opening. In the latter instance, the housing is collapsible and attached, liquid-tight, to the supply tubing so the catheter can be advanced into the vein relative to the needle. In the former instance, the needle is retractable relative to the catheter and housing. In all instances, the length of the portion of the needle disposed within the catheter and extending beyond the free end thereof is less than the length of the liquid flow chamber, so liquid supplied through the hollow interior of the needle will flow into such chamber and then into and through the catheter.