Expression of 6-phosphofructo-2-kinase/fructose-2, 6-bisphosphatase-4 (PFKFB-4) mRNA was studied in different rat organs. Several new unique alternative splice variants of PFKFB-4 mRNA were identified. They have deletions or inserts in fructose-2,6-bisphosphatase region as well as different length and amino acid sequence of C-terminal part. However, 6-phosphofructo-2-kinase catalytic domains were identical in all variants. Moreover, the expression of different alternative splice variants of PFKFB-4 mRNA has shown tissue specificity. Expression of both alternative splice variants of PFKFB-4 mRNA significantly changed in rats treated by methyl tretbutyl ether, ecologically dangerous chemical compound. Results of this investigation indicate a possible role of PFKFB-4 splice isoforms in cell-specific regulation of glycolysis and demonstrate the sensitivity of the regulation of alternative splicing to the action of toxic chemical compounds, in particular methyl tertbutyl ether.