A corn density calibration was developed for a near-infrared transmittance instrument (Infratec 1225). The calibration sample set included 96 corn samples grown in various locations of the United States. Samples were selected by principal component analysis (PCA) from a larger set of 410 samples, representing the 1986 through 1992 crop years. Samples for instrument and temperature stabilization were included in the calibration. The partial least squares calibration was then validated with 35 randomly selected samples not in the calibration sample set. With 14 PCA factors, the standard error of calibration was 0.0173 g/cm3, and the standard error of prediction was 0.0164 g/cm3. Fourteen factors were required because the first 12 reflected the physical correlations of density to protein and density to starch.