In this paper, we review the progress made by the CdTe Thin Film Partnership Reliability Team in developing an accelerated environmental test (AET) methodology that will indicate the expected life of CdTe cells incorporated in a module operated in the field. The primary focus is on test design, cell reliability, and the correlation of indoor accelerated testing with outdoor exposure. The team has emphasized cell-stability issues, and is not examining failure modes such as those involving module packaging, junction boxes, and mounting. The goal is to develop a CdTe cell technology with a 30 yr life, and verify that reliability through AETs. ©1999 American Institute of Physics.