Abstract: A self-releasing pin for a weight training machine of the type having a vertical stack of weights. The self-releasing pin automatically releases a selected number of weights from engagement with a lifting bar when the selected number of weights is returned to a resting position. The main components of the self-releasing pin include a shaft, a bracket, a retaining member, and biasing means. The shaft is capable of reciprocating movement with respect to the bracket through an opening in the bracket. The retaining member is pivotally attached to either the bracket or the shaft to prevent reciprocating movement of the shaft with respect to the bracket. The biasing means are provided intermediate the second end of the shaft and the bracket and bias the shaft to a retracted position.