Photolysis dynamics of monochlorothiophenes (2- and 3-chlorothiophenes) is investigated using positive and negative photoion mass spectrometry combined with the synchrotron vacuum ultraviolet radiation. A dozen of the daughter cations are observed in the time-of-flight mass spectra, and their appearance energies are determined by the photoion efficiency spectroscopy measurements. At the energetic threshold, the concerted process rather than a stepwise reaction for C(4)H(3)SCl(+) → C(2)HSCl(+) + C(2)H(2) and the ring-open isomers of the dehydrogenated thiophene cations (C(4)H(3)S(+) and C(4)H(2)S(+)) formed in C(4)H(3)SCl(+) → C(4)H(3)S(+) + Cl and C(4)H(2)S(+) + HCl are proposed on the basis of the B3LYP/6-311+G(3df,3pd) calculations. The chlorine anion (Cl(-)) is observed as the product of the photoion-pair dissociations in the energy range of 10.70-22.00 eV. A set of valence-to-Rydberg state transitions 12a' → np (n = 6, 7, 8, 9, 10, etc.) and several series of vibrational excitations are tentatively assigned in the Cl(-) spectrum of 2-chlorothiophene in the lower energy range of 10.90-12.00 eV.