Coal fines cleaning wastes (CFCW) were agglomerated with samples of a vegetable oil heated at 150 degrees C for 1-15 days. An agglomeration efficiency index (AEI) which variation depends on the oil agglomeration capability was calculated. Good linear correlations were attained between the AEI values and the viscosity, and the unsaturation degree of the oil monitored by FT-IR and H-1 NMR. Based on the results achieved, the prediction of the agglomeration capability of the waste vegetable oils (WVO) from these properties in relation to the recovery of coal from coal fines cleaning wastes appears feasible. (c) 2006 Elsevier Ltd. All rights reserved.