Because of the relatively high GWPs of HFCs, policy and regulatory actions to reduce, restrict, and eliminate their use are increasing in number. These regulatory actions are leading to the development of unsaturated chlorinated and fluorinated hydrocarbons with lower GWPs. Tradeoffs between GWP, flammability, and specific capacity will need to be made possibly resulting in the need for changes to equipment designs. Some lower GWP refrigerants are already being introduced in many market segments. This presentation provides an overview of these refrigerants and presents the state of understanding and development of these alternatives by their environmental, safety, and design tradeoffs.