As agricultural machinery has become larger and tillage practices have changed in recent decades, compaction as a result of mechanically applied forces such as traction or tillage has caused increasing concern. Amelioration of compaction generally requires some form of deep tillage, increasing costs and energy consumption for the producer, and potentially increasing environmental risks from soil erosion. If compacted areas within fields could be efficiently sensed and mapped, tillage could be targeted to only those areas, resulting in environmental and economic benefits. On-the-go compaction sensors for this purpose are being developed by several research groups. The objective of this research was to evaluate and compare the field performance of two of these compaction sensors. Tests were conducted in two central Missouri fields, with soil types ranging from sandy loam to clay. Both compaction sensors were pulled by a tractor across the field after corn harvest, obtaining data in multiple transects. One sensor measured compaction to a 50-cm depth on 10-cm intervals, while the other also used five sensing elements and obtained data to 40.6 cm on a 7.6-cm interval. Cone penetrometer measurements of compaction were obtained at intervals along each transect for comparison, as were soil core samples for water content and bulk density determination. Data were compared between the two on-the-go sensors and were also related to penetrometer and soil property data. The results of this study will provide information to improve on-the-go sensor design and to relate sensor data to other measures of soil compaction.