This chapter discusses understanding resistance to sterol biosynthesis inhibitor (SBI) fungicides. It starts by first highlighting the current market and trends for this type of fungicide, then goes on to provide a short history of de-methylation inhibitor (DMI) fungicides, one of the four subclasses SBI fungicides can be divided into. This is then followed by an overview of resistance risk and general resistance characteristics of SBI fungicides. A section on mode of action and mechanisms of resistance is also included, followed by a discussion that provides specific examples of resistance to DMIs. The chapter also includes a section that highlights recommended uses for resistance management.