This paper presents an overview of International Space Station (ISS) on-orbit environments exposure flight experiments. International teams are flying, or preparing to fly, externally mounted materials exposure trays and sensor packages. The samples in these trays are exposed to a combination of induced molecular contamination, ultraviolet radiation, atomic oxygen, ionizing radiation, micrometeoroids and orbital debris. Exposed materials samples are analyzed upon return. Typical analyses performed on these samples include optical property measurements, X-ray photo spectroscopy (XPS) depth profiles, scanning electron microscope (SEM) surface morphology and materials properties measurements. The objective of these studies is to characterize the long-term effects of the natural and induced environments on spacecraft materials. Ongoing flight experiments include the U.S. Materials International Space Station Experiment (MISSE) program, the Japanese Micro-Particles Capturer and Space Environment Exposure Device (SM/MPAC&SEED) experiment, the Russian SKK and Kromka experiments from RSC-Energia, and the Komplast flight experiment. Flight experiments being prepared for flight, or in development stage, include the Japanese Space Environment Data Acquisition Attached Payload (SEDA-AP), the Russian BKDO monitoring package from RSC-Energia, and the European Materials Exposure and Degradation Experiment (MEDET). Results from these ISS flight experiments will be crucial to extending the performance and life of long-duration space systems such as Space Station, Space Transportation System, and other missions for Moon and Mars exploration.