Although the chloride and bromide concentrations of the mantle are low, due to its vast size the mantle can be considered as a major reservoir for both elements. It contains approximately one fifth (depending on the source of the data) of all chlorine and bromine on Earth and the isotope composition of its chlorine and bromine is expected to be representative for the chlorine and bromine isotope composition of the Earth after the differentiation of the mantle form the core. For that reason a considerable effort has been made by various research groups to obtain proper, average, values for the chlorine isotope composition of the mantle. In spite of these efforts there still is some serious discussion of what the average chlorine isotope composition of the mantle should be due to the fact that the different research groups concluded towards different values for the average chlorine isotope composition of the mantle. No studies on the bromine isotope composition of mantle material have been made yet, although a few studies have been published that present bromine isotope values that may be related to mantle material and for that reason some suggestions on the possible bromine isotope composition of the mantle may be given.