An obturator assembly for penetrating tissue and being at least partially positionable within a cannula assembly includes an obturator housing, an obturator shaft connected to the obturator housing and defining a longitudinal axis, a penetrating member adjacent the distal end of the obturator shaft and an obturator shield mounted about the obturator shaft and having a distal shield nose. The obturator shield is adapted for longitudinal movement between an extended position where the penetration member is substantially enclosed within the shield nose and a retracted position where the penetrating member is at least partially exposed from the shield nose. A manually manipulative member is mounted to the obturator housing and is adapted for rotational movement about the longitudinal axis and relative to the obturator housing between an initial position corresponding to a first mode of operation where the obturator shield is secured in the extended position and the shield nose is used to penetrate tissue, and a release position corresponding to a second mode of operation operatively releasing the obturator shield to permit the obturator shield to move to the retracted position thereof to expose the penetrating member for penetrating the tissue. The obturator assembly may further include a latch member disposed within the obturator housing. The preferred latch member is in operative engagement with the obturator shield to secure the obturator shield in the extended position thereof. The latch member is actuable to release the obturator shield when the obturator housing is mated with the cannula assembly to thereby permit movement of the obturator shield toward the retracted position provided the manually manipulative member is in the release position. The obturator assembly further includes a release member which is mounted to the obturator housing and operatively coupled with the latch member. The release member is positioned to engage the cannula assembly upon mating o
