Agitator performance in standard vertical vessels with cylindrical shape, dished bottom and zero to four baffles has been the topic of numerous publications. In certain industries, however, horizontal cylindrical vessels with hemispherical ends, divided internally into multiple compartments, are preferred for continuous processes operating at high pressures. Use of standard correlations derived from vertical vessels may lead to incorrect performance predictions for these horizontal vessels, and hence unsatisfactory process results. A number of laboratory trials were undertaken to identify differences in behavior and potential means to improve design for horizontal vessels. Differences with respect to solids suspension, mixing time and residence time distribution were studied. CFD simulations were undertaken and validated against the experimental results.