The long term stability of photographic prints is known to be sensitive to a variety of factors. These factors include the chemical composition of the inks and media, as well as the ambient environmental conditions-light, heat, humidity, and air quality-under which the prints are stored and/or displayed. In order to correlate the results of accelerated testing in the laboratory with what actually happens to a photographic print under long term, real world conditions, it is necessary to better understand the typical ambient environmental conditions under which the prints are being displayed and/or stored. In phase I of this study, light levels, spectral energy distributions, temperatures, and humidities were monitored for 6-12 months in eight homes in each of four cities around the world (Rochester, Los Angeles, London, and Melbourne). For phase II, eight homes in each of four additional cities (São Paulo, Shanghai, Atlanta, and Tokyo) were monitored for 10-12 months. A key finding of these studies is that ambient home display conditions are dominated by relatively low intensity, indirect, window-filtered daylight. The long term temperature and humidity levels averaged close to the commonly cited conditions of 25 °C, 50% relative humidity, with the exception of Shanghai and São Paulo where somewhat higher levels were observed. These results are discussed in the context of designing and interpreting improved accelerated image stability test methods.