A sliding side door assembly (10) for use in a well bore having a side bore. The assembly (10) comprises a housing (12) having a generally tubular shape defining a central axis (X). A side port (28) is formed in the housing (12), and a ball seat (30) is positioned in the housing (12) adjacent the side port (28). A door subassembly (14) is operatively engaged with the housing (12) adjacent the side port (28) and includes a translating sleeve (34) positioned within the housing (12) and a ball sealing member (36) adapted to engage the ball seat (30) of the housing (12). A ball port (40) is formed through the ball sealing member (36). A cooperatively engaged helical track (42) and follower member (44) are provided for translating a driving movement along the central axis (X) through the translating sleeve (34) to a rotational movement of the ball sealing member (36) about the central axis (X). Driving movements acting on the door subassembly (14) can be provided by a standard shifting tool (46). Thus, a first driving movement acting on the door subassembly (14) in a first axial direction along the central axis (X) causes the translating sleeve (34) to rotate the ball sealing member (36) such that the ball port (40) moves into overlapping alignment with the side port (28), thereby opening the side port (28). Similarly, a second driving movement acting on the door subassembly (14) in a second axial direction along the central axis (X) causes the translating sleeve (34) to rotate the ball sealing member (36) such that the ball port (40) moves out of overlapping alignment with the side port (28), thereby closing the side port (28).