Abstract: A catheter is disclosed which is simple to use, avoids the problems with prior catheters, which is fail-safe and fool-proof and one by which the patient cannot injure himself. The catheter comprises a flexible inner tubular member forming a flow duct, snuggly and slidably disposed in an outer tubular member, and having a rounded expansion tip at its inner end comprised of a plurality of prongs biased outwardly and operable to expand and open on inward movement of the inner tubular member in the outer tubular member to a position where the prongs are beyond the inner end of the outer member and to retract on movement of the inner tubular member outwardly in the outer tubular member to a position where at least a portion of the prongs are within the outer tubular member.