Till now the chemical changes in the rhizosphere have not been well known due to difficulties in precise separation of all roots and rhizosphere from bulk soil. In this review paper, the authors describe major chemical changes in the rhizosphere and propose methods of their investigation. These processes may be studied in plants, grown in soil, in sloped (at 45°) rhizoboxes with removable plexiglass lids. On the side of the transparent lid the roots and soil is covered with agar sheet or filter-paper containing specific reagents and indicators. From colour reactions in contactwith root released substances it is possible to assess the following rhizosphere processes: - pH changes (using a prefixed thin agar sheet - 1% agar containing bromocresol purple or bromocresol green - 1% as pH indicator). - Activity of Al (using complexation of Al by the decolouration of polyacrylamide gel or agar containing Aland aluminon). - Mn⁴⁺ to Mn²⁺ reduction (indicated by the decolouration of filter paper impregnated with Mn oxide). - Fe³⁺ to Fe²⁺ reduction (indicated by the formation of a red coloured complex between Fe²⁺ EDTA and BPDS in an agar medium). - The activity of acid phosphatase (indicated by the formation of a red complex on filter paper containing 1-naphtyl phosphate as substrate and Fast Red TR as specific indicator).