Compacted soils generally have higher bulk density, increased mechanical impedance, and lower levels of water movement and oxygen than soils that are not compacted. Our objectives were to measure soil physical properties of soil under tilled and no-till soil management and to investigate the relationship between these properties and grain yield in corn. Plots were established on a Barnes sandy clay loam soil (fine-loamy, mixed, superactive, frigid Calcic Hapludoll) in 1997. Main plots were soil management with tillage (fall chisel plow and spring disk) or no-till treatments. Soil penetrometer, soil bulk density, and soil moisture measurements were taken within plant rows at the V6 leaf development stage. Relationships between soil penetrometer resistance at different soil depths and corn grain yield were assessed by calculating Pearson's correlation coefficients. In no-till plots, soil penetration resistance was very close to 1.5 MPa in the top 30 cm, while at deeper depths it ranged from 1.6 to 2.3 MPa. In tilled plots, soil penetrometer resistance ranged from 0.5 to 1.2 MPa in the top 15 cm of the soil profile and 1.2 to 1.5 MPa from 25 to 60 cm soil depth. Correlation coefficients were calculated with grain yield and soil penetrometer resistance (1 to 60 cm soil depth at 5 cm increments) as variables. With the exception of 15 and 20 cm depths (in the region of the plow pan in the tilled plots), probabilities associated with r were highly significant over all depths. Correlation coefficients ranged from -0.47 to -0.67 across soil depths. These coefficients suggest that grain yield was negatively correlated to soil penetrometer resistance. These data reveal the importance of minimizing soil compaction, especially when using no-till soil management.