A releasably locking dilator and sheath assembly and methods for releasing thedilator from the sheath and longitudinally splitting the sheath. The assemblyincludes adilator having a dilator hub and a sheath having a sheath hub. The sheath hubhas a valveand two opposing winged tabs, each tab having a perpendicular portion and anangledportion, as well as having a female locking portion. The dilator hub has amale lockingportion designed to engage the female locking portion of the sheath hub. Thedilator isreleased from the sheath by rotating the dilator 90° in relation to thesheath and pulling thedilator out of the sheath. The sheath is longitudinally split by creating acouple on each ofthe winged tabs thereby forcing the sheath and the sheath hub to splitlongitudinally. Withthe sheath and sheath hub and valve split longitudinally, the sheath isremoved fromaround a catheter while leaving the catheter in place.
