Well control refers to drilling techniques that keep formation fluids from erupting at the surface. There are three levels of well control: 1) drilling mud, 2) annular preventer and 3) mechanical rams within a blowout preventer stack (BOP). Maintaining mud pressure slightly higher than formation pressures is non-disruptive and is the first line of defense against a blow-out. The annular preventer is used to shut-in a well and to remove a kick. Mechanical rams (pipe, shear, blind) are used as a last resort. This chapter covers the application of these well control techniques.