PRODUCTION OF ETHYLENE HOMOPOLYMERS HAVING A SPECIFIC DENSITY BY POLYMERIZATION OF ETHYLENE UDER THE ACTION OF ORGANIC PEROXIDES AND OXYGEN AS FREE-RADICAL-GENERATING POLYMERIZATION INITIATORS AND OF POLYMERIZATION MODIFIERS AT ELEVATED TEMPERATURE AND SUPERATOMSPHERIC PRESSURE IN A TUBULAR REACTOR HAVING TWO SUCCESSIVE REACTION ZONES, A MIXTURE OF ETHYLENE, POLYMERIZATION INITIATOR AND POLYMERIZATION MODIFIER BEING INTRODUCED CONTINOUSLY AT THE BEGINNING OF EACH REACTION ZONE. OXYGEN AS POLYMERIZATION INITATOR AND A POLYMERIZATION MODIFIER HAVING A SPECIFIC RELATIVELY LOW CS VALUE ARE USED IN THE FIRST REACTION ZONE, AND AN ORGANIC PEROXIDE AHVING A SPECIFIC HALF VALUE TEMPERATURE AS POLYMERIZATION INITIATOR AND A POLYMERIZATION MODIFIER HAVING A SPECIFIC RELATIVELY LOW CS VALUE ARE EMPLOYED IN THE SECOND REACTION ZONE. THE ETHYLENE HOMOPOLYMERS OBTAINED HAVE A WIDE MOLECULAR WEIGHT DISTRIBUTION AND ARE PRACTICALLY DEVOID OF VERY HIGH MOLECULAR WEIGHT CONSTITUENTS.