Co-liquefaction of oil shale kukersite and willow Salix viminalis blends by hydrous pyrolysis in supercritical water was studied under the conditions of 380 degrees C, 4 h, 38 MPa, and water/blend ratio 3/1 g/g. The actual yields of the consecutive products of extraction with various solvents did not agree with the additive values calculated by proportional contributions of the blend components. At any share of the components (x(A), x(B)), the synergy (Delta) in the yields of the pyrolysis products estimated was proportional with the product of the shares of the components in the blend according to the equimolecular synergy model, Delta = delta x(A)x(B). The values of the synergy factors, delta, decreased in the row of the products as follows [%(g/g)(-2)]: the oil soluble in benzene 62, acetone 11, water 9, and diethyl ether 5.6, solid residue -9.6 and the sum of gas and pyrogenetic water -79. The main increase in the yield of benzene solubles was result of the positive synergy in the yield of high polar heterocompounds, revealing the synergy factor 69%(g/g)(-2). (c) 2014 Elsevier Ltd. All rights reserved.