. The use of simplex algorithm for determination of soil aggregation extreme changes has been presented. It enables to find the range of changes of the soil aggregates stability index for one-directional aggregation changes and assigned criterion of the soil aggregation stability evaluation. The basic data for calculation of the ranges of changes are distributions of soil aggregate frequencies before and after the occurrence of the destruction factor. The problems of existence of feasible solutions and their uniqueness have been also discussed. It has been found that simplex algorithm is suitable for calculation of extreme values of aggregates stability index (ASI).