The International Satellite Cloud Climatology Program (ISCCP) C1 analysis of cloud amount has been compared to an analysis utilizing high resolution AVHRR imagery for twelve days in July 1983 over part of the eastern Atlantic, Western Europe and North Africa. The AVHRR analysis relies upon five individual tests requiring four spectral channels at the full 1·1 km resolution. The mean C1 cloudiness was found to be about 6 per cent greater than that of the AVHRR. However, the spatial and temporal variations in the AVHRR were found to be well simulated by the C1 analyses. Much of the difference in the means may be explained by the fact that the AVHRR cloud fractions were weighted by the fraction of partially filled sky, whereas the C1 values were not.