On June 10 and July 7, 2003, the National Aeronautics and Space Administration (NASA) launched two spacecraft from Cape Canaveral, Florida, for 6-month flights to the Red Planet, Mars. The two Mars Exploration Rover spacecraft landed safely on the planet on January 3 and 24, 2004. Prior to the successful launch, both of the spacecraft were involved in a comprehensive test campaign that included development, qualification, and protoflight test programs. Testing was performed to simulate the environments associated with launch, interplanetary cruise, landing on the planet, and Mars surface operations. Unique test requirements included operating the spacecraft while the chamber pressure was controlled to simulate the descent to the planet from deep space, high-impact landing loads, and rover operations on the surface of the planet at 8 Torr and -130 °C (-202 °F). This paper will present an overview of the test program that included vibration, pyroshock, landing loads, acoustic noise, thermal-vacuum, and solar simulation testing at the Jet Propulsion Laboratory (JPL) Environmental Test Laboratory facilities in Pasadena, California.