Low-temperature sealing with elastomers is critical in both arctic regions and subsea valves. Additionally, sour gas or hydrogen sulfide is increasingly being found in oil and gas production as more challenging fields are being developed throughout the world. Valves are being asked to perform in sour conditions that involve expanded temperature ranges along with pressure cycles. The performance of the seals in a valve is often the limiting factor in a valve’s performance; knowing the effects of low-temperature and sour gas on elastomers is critical in oil and gas valve applications. While many engineers are comfortable specifying metals for valves in sour environments, they may not have an understanding of the performance limitations of the elastomers. The limitations for elastomers that will determine a successful seal in a valve often include properties such as oil resistance along with high- and low-temperature performance. Following is a review of these limitations from the perspective of low-temperature performance and sour gas resistance. Additionally, strategies will be provided to ensure the best seals are selected for a given application.