The carbocationic polymerization of norbornadiene (NBD) using the 2-chloro-2,4,4-trimethyl-pentane (TMPCl)/ diethyl-aluminium chloride (Et2AlCl) initiating system in ternary solvent mixtures (CH3Cl/CH2Cl2/hexane) lead to soluble poly(norbornadiene)s (PNBDs) with molecular weights Mn ranging up to ~6,000 g/mol and polydispersities (Mw/Mn) down to ~1.3. Slow initiation and coupling reactions between PNBD chains were observed, but the polymerization was controlled overall. After longer reaction times, multimodal weight distributions could be observed. More control could be achieved by using proton traps, e.g. di-tert-butyl pyridine.