Abstract The autocorrelation function was used to determine the average correlation coefficients in the electron diffraction intensities from the Cornell apparatus. Weight matrices with off-diagonal elements were used in least squares refinements of one average intensity curve obtained from several diffraction photographs in each of three experimental configurations, of three average intensity curves, each of one experimental configuration, and of fifteen intensity curves. The standard deviations are 2.2 to 4.0 times greater than those obtained using diagonal weight matrices. The autocorrelation function gives the same estimate of data correlation as the method of Seip, Strand, and Stølevik. Standard deviations calculated by the method of Murata and Morino are 70–80% of those obtained from the autocorrelation function and the Norwegian method. The correlation in the Cornell, Oslo and Manchester electron diffraction data is approximately equal and considerably greater than that reported by the Tokyo group.