Calcium channel β subunits have marked effects on the trafficking and on several of the biophysical properties of all high voltage activated calcium channels. In this article I shall review information on the different genes, on the structure of the β subunits, and on their differential expression and post-translational modification. Their role in trafficking and assembly of the calcium channel heteromultimer will be described, and I will then review their effects on voltage-dependent and kinetic properties, stressing the differences between palmitoylated β2a and the other β subunits. Evidence for effects on calcium channel pharmacology will also be examined. I shall discuss the hypothesis that β subunits can bind reversibly to calcium channels, and examine their role in the G protein modulation of calcium channels. Finally, I shall describe the consequences of knock-out of different β subunit genes, and describe evidence for the involvement of β subunits in disease.