All plant cells produce fatty acids from acetyl-CoA by a common pathway localized in plastids. Although the biochemistry of this pathway is now well understood, much less is known about how plants control the very different amounts and types of lipids produced in different tissues. Thus, a central challenge for plant lipid research is to provide a molecular understanding of how plants regulate the major differences in lipid metabolism found, for example, in mesophyll, epidermal, or developing seed cells. Acetyl-CoA carboxylase (ACCase) is one control point that regulates rates of fatty acid synthesis. However, the biochemical modulators that act on ACCase and the factors that in turn control these modulators are poorly understood. In addition, little is known about how the expression of genes involved in fatty acid synthesis is controlled. This review evaluates current knowledge of regulation of plant fatty metabolism and attempts to identify the major unanswered questions.