Transmission line foundations provide the interlinking component between the support and in-situ soil and/or rock. The interrelationship between the support type and the applied foundation loadings are considered, together with the methods of determining the engineering properties of the in-situ soil and/or rock. Two principal categories of foundations have been considered: separate and compact. The major types applicable to each category are reviewed e.g. monoblock, spead, drilled shaft, pile, anchor, direct embedment of poles, etc…