In downhole applications, most progressive cavity (PC) pump failures involve the stator elastomer and often result from chemical or physical elastomer breakdown induced by the wellbore environment. Successful use of PC pumps, particularly in the more severe downhole environments, requires proper elastomer selection and appropriate pump sizing and operation. PC pump manufacturers continue to develop and test new elastomers; over time, these efforts have resulted in performance improvements and an expanded range of practical applications. Despite this success, the elastomer component still continues to impose severe restrictions on PC pump use, especially in applications with lighter oils or higher temperatures. The performance of an elastomer in a PCP application depends heavily on its mechanical and chemical properties.