Environmental testing data are presented and discussed in relation to the suitability of CuInSe2 (CIS) as a durable photovoltaic material and to the Interim Qualification Tests and Procedures for Terrestrial Photovoltalc Thin-Film Flat-Plate Modules (IQTP). Groups of modules having no significant change after ten humidity-freeze cycles are reported. Heating during module packaging or during environmental testing to temperatures above those normally encountered by modules in outdoor service may introduce a temporary power loss; the power recovers with time to near the initial power. Data indicate that temperature alone, rather than temperature combined with humidity, causes the temporary power loss and that CIS is not inherently sensitive to humidity. Hermetic seals are not in general necessary for CIS materials. The IQTP may improperly indicate poor performance if the temporary power loss is not considered in electrical performance testing between different sections of the environmental test procedures and at the end of all environmental tests. Data are not available to validate accelerated testing as a means of predicting long-term in-service performance; however, correlations between outdoor and accelerated testing are seen.