Lock-open mechanism for surface controlled subsurface safety valves. A lock-open sleeve can be positioned by wireline techniques to hold open the valve closure means for a subsurface safety valve. The operating tube of the safety valve can be used to return the valve closure means to normal operations. One embodiment of the present invention is particularly useful as a well tool which can readily be attached to the lower portion of presently available flapper type safety valves. Alternative embodiments of the present invention can be built into both ball type and flapper type safety valves as an integral part of the complete safety valve assembly.