Modern ooid sand particles were experimentally compacted at 150 degrees , 200 degrees C, and at pressures varying between 824 and 1,565 kg/cm 2 , consistent with overburden of 3.5 to 6.5 km. Bulk-volume reduction, under the above experimental conditions, was more substantial than usually believed: 21 to 26 percent. Particle breakage and deformed particle contacts developed that are comparable to those reported for oolites from the rock record. Pressure solution can be successfully produced. Initial pore-volume reduction through mechanical grain adjustments and ultimate pressure solution are major processes in the diagenetic evolution of limestones. This appears to contribute to the solution of the mass balance problem involved in the large porosity reduction that occurrs when carbonate sediments lithify. Additionally, ooids were noted to have been plastically deformed, giving rise to longitudinal and concavo-convex contacts.--Modified journal abstract.