Transmission expansion planning (TEP) has faced a significant change since the introduction of deregulation. It becomes even more complicated. Algorithms have to be changed to meet new challenges. This paper organizes and classifies existing TEP algorithms in both regulated and deregulated environment so as to facilitate other research works in this area. Besides, two suggestions have been made for the TEP approach in the future. Firstly, some standard elements are inevitably needed in TEP algorithms. Those standard elements can be left to other researchers for specialization. Research effort can, therefore, be saved, if only TEP algorithm has to be considered. Secondly, specific market regulations and conditions should be included in the future TEP algorithm so as to turn the algorithm from an academically feasible one into a commercially feasible one