Errors in the standard cloud fraction products produced by the Moderate Resolution Imaging Spectroradiometer (MODIS) and the Multi-angle Imaging SpectroRadiometer (MISR) on EOS-Terra were examined using 15 m resolution data from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER). Relative to 124 ASTER scenes containing only trade wind cumuli and having an average cloud fraction of 0.08, MODIS and MISR overestimated cloud fraction by 0.18 and 0.36, respectively. For non-sunglint scenes, MODIS and MISR overestimated cloud fractions by 0.02 and 0.24, respectively. Systematic dependences in the MODIS and MISR cloud fractions with ASTER cloud fraction were observed. Large RMS errors in MODIS and MISR cloud fractions were observed because of variations in the spatial distribution of clouds, suggesting it may be difficult to decouple long-term changes in cloud fraction from satellites from true changes in the spatial distribution of clouds.