abstract: The use of simplex algorithm for determination of soil aggregation extremal changes is presented. For one-directional aggregation changes and assumed in this paper criterion of the soil aggregation stability evaluation it enables to find the range of changes of the soil aggregates stability index. The basic data for calculation are distributions of soil aggregate frequencies before and after destruction factor occurrence. It was also discussed the existing problems of possible solutions and their uniquenesses. It stated that simplex algorithm is suitable for calculation of extreme values of aggregates stability index (ASI).