Mild thermal cracking of vacuum residue is used in an oil refinery for 'bottom of the barrel' upgradation in the form of visbreaking. Lab scale studies were conducted in a batch reactor to study the cracking behavior of vacuum residues at mild severity conditions in terms of lumping of distillate fractions. Four residual feedstocks of Indian and Middle East origin, being processed in Indian refineries were studied for five different residence times between 3 and 15 min and four different temperatures ranging between 400 and 430 degrees C. A five lumped and seven parameter kinetic model has been developed for the prediction of yield of products. The lumping scheme chosen was based on the most value added products, i.e., gas, gasoline, light gas oil (LGO) and vacuum gas oil (VGO). Delplot analysis has been used for determining reaction pathways. (c) 2005 Elsevier B.V. All rights reserved.