AbstractFor a number of applications the use of polyethylenes with a high polydispersity is recommended. In order to prepare such grades polymerisation tests were performed in a stirred autoclave in laboratory scale. The autoclave was run continuously at 1800 bar in the range of 210 to 285°C with 60 s residence time. Difunctional peroxides with identical and with different substituents on both OO groups were tested. For comparison, monofunctional compounds from industrial processes were used. The concentration of the peroxides in the feed was varied between 3 and 60 mol ppm.By GPC, polydispersities of 5 to 9, comparable to those of commercial polyethylenes, were measured on the samples produced with the monofunctional peroxides. Distinctly higher polydispersities of up to 13 were achieved by the use of the difunctional peroxides, especially with the symmetrical compou