The International Satellite Cloud Climatology Project (ISCCP) B1 data, which was recently rescued at the National Atmospheric and Oceanic Administration's National Climatic Data Center (NOAA/NCDC), is a potentially great resource in the study of the earth's climate. The ISCCP B1 data representing geostationary imagery from infrared (IR), visible and IR water vapor sensors from satellites around the world provides global 3 hourly snapshots from 1979 to present at 10 km spatial resolution. ISCCP B1 data will be employed in the reprocessing of the cloud products resulting in a higher resolution ISCCP cloud climatology, surface radiation budget (SRB), etc. Among other applications, the B1 data has been successfully employed in hurricane research and precipitation monitoring in data-sparse regions. While the IR and water vapor channels of B1 data have been well-calibrated, assessment of the visible channel shows gaps (such as pre-1983 years) and inconsistencies. The present study aims to address these issues and maximize the calibration accuracy by cross-calibrating with the inter-calibrated Advanced Very High Resolution Radiometer (AVHRR) reflectance data from the AVHRR Pathfinder Atmospheres Extended (PATMOS-x) data set. Since the reflectance calibration approach followed in the PATMOS-x data set is radiometrically tied to the observations from the National Aeronautics and Space Administration's (NASA) Moderate Resolution Imaging Spectroradiometer (MODIS) imager instrument, the present inter-calibration scheme yields calibration coefficients consistent with MODIS.