NULL Convention Logic (NCL) is one of the mainstream asynchronous logic design paradigms. NCL circuits use threshold gates with hysteresis. In this chapter, the transistor-level CMOS design of NCL gates is investigated, and various gate styles are introduced and compared to each other. In addition, a novel approach to design static NCL gates is introduced. The new approach is based on integrating each pair of pull-up and pull-down transistor networks into one composite transistor network. The new static gates are then compared to the original ones in terms of delay, area, and energy consumption. It will be shown that the new gate style is significantly faster with negligible area and energy overhead.