Suction caissons are becoming a widely used foundation system for mooring offshore platforms in deep water. However, there is a significant lack of measured data on the behavior of suction caissons subjected to lateral loads applied below the mudline. In this study, laboratory-scale tests were conducted with horizontal loads applied to a model caisson installed in normally consolidated kaolin. The results are useful in supporting the development of improved analytical methods for the design of these structures. Two deposits of normally consolidated kaolinite were constructed at the University of Texas at Austin. The properties of these test bed soils were characterized prior to testing the model caisson. Nine horizontal load tests were conducted in one of the soil deposits. Prior to installation of the caisson, a loading cable was attached to a point on the padeye bar along the lower half of the caisson. The 100-mm diameter caisson prototype was installed to half its length using dead weight, and full penetration (800-mm) using suction. The loading cable was then pulled to a horizontal position. Excess pore water pressures were allowed to dissipate for 48 hours to achieve full set-up prior to loading. A computer-controlled motor was used to load the caisson to failure rapidly under undrained soil conditions. Presented measurements include: excess pore water pressures on the caisson walls, horizontal and vertical displacement of the top cap, horizontal displacement of the padeye, and tilt of the caisson. The maximum horizontal capacity occurred when the load was applied at about two-thirds of the caisson depth below the mudline. The caisson cap tilted toward or away from the load cable when it was attached above or below the optimal loading point, respectively.