ICOS and DIAMOND are two LC solvent optimization software packages commercially available from Hewlett-Packard and Unicam, respectively. U-83,757 and various related compounds were chosen as the test mixture for the comparison of these systems. Chromatographic data were collected on both systems using the same 10 mobile phase compositions, equally spaced across an iso-eluotropic plane. The comparison focused on determining the performance of both packages with respect to the prediction of the mobile phase composition required to achieve an optimal separation. Both software systems are semi-automatic, with differing amounts of operator involvement required and employing slightly different approaches to interpolating peak movements between the 10 sets of data. The predicted optimal solvent compositions are evaluated in terms of the extent the information collected across the iso-eluotropic plane was used by the various algorithms in the two systems. Our results demonstrate the importance of comprehending the component operations involved in and the limitations of any software package that is used in analytical development. The operator should always remember that both systems are simply tools and design experiments appropriately, since the quality of the final result is highly dependent on a combination of the operator's objective, the capability of the system and the appropriateness of the data input.