To modify a coal tar pitch, a PET-plant glycol-regeneration (waste) residue (GRR), i.e., a mixture of esters and oligoesters of terephthalic acid and mono and diethylene glycols (acid no. 3-6 mg KOH/g, viscosity (eta) 117 Pa.s (25degreesC), density 1.165 g/mL (89degreesC), ignition temp. (135degreesC), was blended (GRR 0-30%, 160degreesC, 0.5 h) with a coal-tar pitch (ball-and-ring soft. p. 68.5degreesC, toluene-insolubles 18.4%., benzo[a]pyrene 1.83%). In addition to pitch structure changes, the modification involved substitution of H atoms in benzopyrene via C- and O-alkylations (by unsatd. polyester resin and poly(oxyethylene)diols, resp.). Flow curves (log of yield value (tau) = A(1) log D + A(o) over T = 90-150degreesC and shear-strain rate D = 0-1000 s(-1)), eta vs. T and D, softening p., and penetration were measured for the blends. At =20% GRR, the flow curves were similar to those of the virgin pitch, viz., non-Newtonian with A(1) values of <0.9 to 1; at 30% GRR, A(1) = 0.6. The share of the structural in the apparent viscosity always exceeded 50016; in the 30% GRR blend, it exceeded 90%. With the modifier added, the bitumen assumed a gel structure. As the GRR proportion was increased, the viscous flow activation energy evaluated from In η vs. 1/T straight-line plots fell, Le., the GRR plasticized the pitch and continued to weaken the interactions of the components. At higher temperatures, pseudoplastic properties were less pronounced. Group analyses (Me2CO- and toluene-(in)solubles) and penetration data confirmed the GRR-effected changes in the physical structure of the pitch.