text: SHIFTCOR is an automated protein chemical shift correction program that uses statistical methods to compare and correct predicted NMR chemical shifts (derived from the 3D structure of the protein) relative to an input set of experimentally measured chemical shifts. SHIFTCOR uses several simple statistical approaches and pre-determined cut-off values to identify and correct potential referencing, assignment and typographical errors. SHIFTCOR identifies potential chemical shift referencing problems by comparing the difference between the average value of each set of observed backbone (1Hα, 13Cα, 13Cβ, 13CO, 15N and 1HN) shifts and their corresponding predicted chemical shifts. The difference between these two averages results in a nucleus-specific chemical shift offset or reference correction (i.e. one for 1H, one for 13C and one for 15N). In order to ensure that certain extreme outliers do not unduly bias these average offset values, the average of the observed shifts is only calculated after excluding potential mis-assignments or typographical errors.