The authors are reporting on an investigation of the feasibility of direct determination ofthe active state of an atmospheric resid on the basis of the disperse-phase particle size, for comparison with results obtained by the indirect methods that had been used previously for this purpose. As objects of investigation the authors selected atmospheric resids from Tyumen' and Tuimzy crudes, as proposed at the Novo-Ufa Petroleum Refinery. As the modifier a solvent extract obtained in treating the No. III lube cut from a mixture of these two crudes was used. The characteristics of the stocks used in this investigation are also listed.