All over the world, including Poland, interest in the organic farming is growing. It is based on an attempt to minimize human impact on the environment while maintaining the natural functionality and productivity of the agricultural system. At the same time, every human activity in the natural environment results in greater or lesser changes in the soil ecosystem. Organic farming also has an impact on physical and chemical parameters and soil biological activity. These changes should be monitored and considered in the context of long-term land management. This review focuses on the impact of the organic farming system on soil biological activity and diversity of soil microorganisms.