A process for preparing polyethyleneamines of formula NH2-(CH2-CH2-NH-)pH wherein p is at least 3 and wherein one or more —NH-CH2-CH2-NH— units may be piperazine units and/or ethylene urea derivatives of these compounds, includes reacting monoethylene glycol with an amine-functional compound having at least two —NH— units, of which at least one is selected from primary amine groups and cyclic secondary amine groups, in the presence of a carbon oxide-delivering agent. The amine-functional compound includes at least one —NH-CH2-CH2-NH— unit, and one or more —NH-CH2-CH2-NH— units may be in the form of cyclic ethylene urea moieties, piperazine moieties, or linear ethylene urea moieties. The molar ratio of amine-functional compound to monoethylene glycol is above 1.2:1 and the molar ratio of carbon oxide delivering agent to —NH-CH2-CH2-NH— units is at least 0.5:1. The process makes it possible to obtain ethylene amines and derivatives thereof without using ammonia or metal-containing catalysts.