Abstract: A one-trip whipstock milling system is disclosed which allows for setting of a packer or plug which is run in as part of the bottomhole assembly, in conjunction with orientation instrumentation, a whipstock, and a one-trip milling system connected to the whipstock. The assembly is run-in the hole together and inserted to the desired depth. With the orientation of the whipstock known from the down-hole instrumentation, the preferred embodiment involves pressurization of the wellbore to actuate the packer assembly. Having set the packer at the proper orientation and depth, the milling immediately begins and continues in a continuous effort until the window is fully milled, at which point the milling equipment and orientation equipment are withdrawn from the wellbore.