Abstract: An improved safety device is provided for protecting medical personnel and the like against needle stick injuries and/or exposure to communicable diseases or other harmful agents. The safety device comprises an elongated protective sleeve supported by front and rear bearing members for sliding movement about a medical needle and its associated support structure, such as a support hub or barrel. The protective sleeve is slidable in a stable manner from a first position with the pointed end of the needle safely retracted within and shielded by the front bearing member to a second position with the needle projecting through and beyond the front bearing member for normal use. After use, the sleeve is slidable to a third position derailing the pointed needle end from the front bearing member, and exposing a visual indicator to indicate that the needle has been used.