Two main considerations govern the design of pavements. The first involves the design of a physical structure, that is capable of sustaining the applied loads. The second aspect of the problem is concerned with the design of materials that constitute the pavement structure. This investigation involves the latter aspect of the design. Soil-aggregate mixtures are commonly used as base material under flexible and rigid pavements. This study evaluated the effect of varying the amount of material retained between the No. 30 and No. 200 sieves on the stability of soil-aggregate mixtures. For the extreme case, the test mixtures were completely devoid of material between the No. 30 and No. 200 sieves. The study was confined to materials that conform essentially to Indiana specification No. 53 aggregate. The testing program included both gravel and crushed stone mixtures. A number of different soil binders (material passing the No. 200 sieve) were used. These binders were classified as non-plastic, low plastic and high plastic tines. To evaluate the effect of the material retained between the No. 30 and No. 200 sieves on the stability of various aggregate-soil binder combinations used in this study, the following tests were used: 1. Atterberg limits tests; 2. Compaction tests; 3. CBR test; 4. Texas trtaxial compression test; 5. Permeabilit) test.