Abstract: A well casing hanger assembly for releasably connecting first and second well casings to and from each other in a well by longitudinal movement of the first member. The first member includes an annular recess in its peripheral surface and a stop shoulder is positioned at each end of the recess and a resiliently expandable and contractible locking ring is positioned in the recess for engagement with a locking notch on the second member. A protrusion is positioned in the recess and initially coacts with an opening in the locking ring. An improved releasable holding means is provided for initially preventing the locking ring from moving axially on the first member until the locking ring expands and engages the second member.