A valve assembly for use in a wellbore of an oil, gas or water well, having a valve seat to seat a valve closure member such as a ball, and a control member that is adapted to cycle the valve assembly between first and second configurations of the valve assembly when the ball is seated on the seat. The valve assembly may be adapted to return the valve assembly to the first configuration when the valve closure member is seated on the seat, and may repeatedly, continuously and/or sequentially cycle from first to second configurations and back to first configuration to open and close an outlet port while the same valve member is seated on the seat. The valve seat may comprise first and second seat members and retain the ball in a cleft between the first and second seat members.