The photochemistry of 1,1-dimethyl- and 1,1,3,4-tetramethylstannacyclopent-3-ene (4a and 4b, respectively) has been studied in the gas phase and in hexane solution by steady state and 193 nm laser flash photolysis methods. Steady state (lamp) or semi-preparative laser photolysis of the two compounds results in the formation of 1,3-butadiene (from 4a) and 2,3-dimethyl-1,3-butadiene (from 4b) as the major products, suggesting that cycloreversion to yield dimethylstannylene (SnMe₂) is the main photodecomposition pathway of these molecules. Indeed, the stannylene has been trapped as the Sn-H insertion product upon photolysis of 4a in hexane solution containing trimethylstannane. Flash photolysis of 4a in the gas phase affords a transient absorbing in the 450-520 nm range that is assigned to SnMe₂ on the basis of comparisons of its spectrum and reactivity to those previously reported from other precursors. Flash photolysis of 4b in hexane solution affords results consistent with the initial formation of SnMe₂ (l_max ~ 500 nm), which decays on the microsecond timescale to form tetramethyldistannene (5b; l_max ~ 470 nm). The latter then decays over the next ca 50 microseconds to form at least two other longer-lived species that are assigned to higher SnMe₂ oligomers. Time-dependent DFT calculations in support of the spectral assignments for SnMe₂ and Sn₂Me₄ are reported, as well as calculations examining the variation in the bond dissociation energies with substituent (H, Me, and Ph) of disilenes, digermenes and distannenes, in order to address the possibility that dimerization of SnMe₂ proceeds reversibly. Addition of millimolar amounts of methanol leads to reversible reaction with SnMe₂ to form a new transient absorbing at l_max ~ 360 nm, which is assigned to the Lewis acid-base complex between the stannylene and the alcohol. These studies represent the first direct observations of both SnMe₂ and Me₂Sn=SnMe₂ in solution.