Abstract: A tubular adaptor is adapted to be interposed between an intravenous catheter and a needle carried by a tube holder for housing an evacuated tube for blood-sampling purposes. The adaptor is readily separable from the catheter by means of a tapered-socket fitting, and in this manner, either blood-sampling or intravenous-feeding may be accomplished at the same catheterized situs. The needle and evacuated tube assemblage are isolated from the situs by means of the adaptor and catheter. The flexibility of the catheter tube also serves to isolate the assemblage from the situs whereby adverse effects created by the assemblage during sampling procedures are not impressed upon the situs.