We discuss oblique spherical aberration, its balance, and its control. Several ways to mitigate this aberration are listed and some lens design examples are presented. The variation of oblique spherical aberration as a function of index of refraction and the shape factor of a thin lens is also presented. It is argued that controlling the amount and distribution of spherical aberration propagating in a lens system can be an important mechanism for mitigating oblique spherical aberration. The control of oblique spherical aberration is illustrated with a double Gauss lens, with lenses for microlithography, and with a lens for mobile phones.