In this chapter, different types of transitions designed to convert conventional transmission lines to SSPP transmission lines (i.e., quasi-TEM mode to SSPP mode) are studied. The transitions that show excellent transmission efficiency over a wide frequency range and a good transition occupation ratio are discussed in this chapter. Different transitions from conventional transmission lines such as microstrip lines, coplanar waveguide, and slot lines to SSPP transmission lines are presented. Advantages and disadvantages of groundedGrounded structures and ungrounded structures are also included in this chapter.