A portable, prototype NIR spectrophotometer was redesigned for improved accuracy and ease of use. The instrument was used to estimate soil organic carbon (or organic matter), moisture content, and clay content of 30 Illinois surface soils in the laboratory. Accuracy of carbon estimation by partial least squares regression was similar to that obtained with the previous design. The unit was also used to estimate soil organic carbon through the profile of two Illinois soils. Results of this test were promising, but need to be verified over a wider range of soils.