This study validates cloud top pressure measurements from the GOES-8 sounder. Data from the March 2000 Intensive Operational Period (IOP) from the Department of Energy's (DOE) Atmospheric Radiation Measurement (ARM) program Cloud and Radiation Testbed (CART) site near Lamont, OK were used as the validation source. This includes cloud top height derived from a ground-based combination Micropulse Lidar/Millimeter Cloud Radar (MPL/MMCR). Hourly cloud top pressure measurements from the sounder were first converted to height using radiosondes launched within six hours. These sounder cloud height measurements were compared to time averaged MPL/MMCR cloud top heights. The data were filtered to make sure only single layer cloud decks were compared. After eliminating multiple cloud levels, the comparison shows high correlation coefficients (>0.9) between the two independent measurements. The measurements also agree upon the existence or non-existence of a cloud three-fourths of the sampled time.