The invention relates to a valve assembly which includes at least one, but typically two, balls located along a passage and which balls can be moved between open and closed positions to selectively control the passage of fluid along the passage. The valve assembly includes at, at least one end thereof, a retaining assembly which allows the effective sealing against one surface of a ball and retention of the ball in position. A sealing assembly is also provided when two balls are provided, which allows effective sealing to be achieved and at least one of the two trunnions which allows each of the balls to be mounted within the valve body is located only internally of the valve body. The components of the valve assembly can in one embodiment all be inserted into and located within the valve body from one common end.