The photochemistry of perchlorinated cycloheptatriene (CHTCl8) has been studied by means of ultrafast pump-probe, transient anisotropy and continuous UV-irradiation experiments in various solvents as well as by DFT calculations. After UV-excitation to the 1A ''-state, two competing reactions occursa [ 1,7]-sigmatropic chlorine migration via two ultrafast internal conversions and a [ 4,5]-electrocyclization forming octachlorobicylo[3.2.0]hepta-[ 2,6]-diene. The first reaction has been studied by excitation with a 263 nm femtosecond-laser pulse. Pump-probe experiments reveal a first, solvent-independent time constant, tau(CHTCls)(1) = 140 fs, that can be associated with the electronic relaxation of the 2A'-1A '' transition, while a second one, tau(CHTCls)(2), ranges from 0.9 to 1.8 ps depending on the polarity of the solvent. This finding is consistent with a [ 1,7]-chlorine migration during the 1A'-2A' transition where the migrating chlorine atom is partly negatively charged. The charge separation has also been confirmed by DFT calculations. Transient anisotropy measurements result in a time zero value of r(0) = 0.35 after deconvolution and a decay constant of tau(a)(1) = 120 fs, which can be explained by vibrational motions of CHTCl8 in the electronically excited states, 1A '' and 2A'. After continuous UV-irradiation of CHTCl8, octachlorobicylo[ 3.2.0] hepta-[ 2,6]-diene is primarily formed with a solvent-dependent yield. From these investigations, we suggest a relaxation mechanism for CHTCl8 after photoexcitation that is comparable to cycloheptatriene.