The processes of homo-oligomerization and co-oligomerization of dicyclopentadiene (DCPD) were investigated on the laboratory and pilot-plant scale under controlled isothermal or boiling conditions. The effect of reaction conditions on the quality of products and on the length of the reaction run was studied. The oligomerization of DCPD can proceed by two different mechanisms - the Diels-AIder polyaddition at temperatures below 200 degreesC and by thermal oligomerization at temperatures close to 260 degreesC. Products obtained by these two mechanisms differ significantly in their physical properties. Realistic models of Diels-Alder and thermal oligomerization processes considering reversible reaction kinetics and vapor-liquid-phase equilibrium were developed. The effects of pressure and the presence of high-boiling solvent on the Diels-Alder oligomerization process and product properties are discussed.