Low-energy electron-energy-loss spectra of 6,6’-dimethylfulyene deposited on a thin film of solid argon are measured at a temperature of 16 K. The spectra make it possible to locate the lowest triplet state with an onset of the transition band at 1.9 eV and a vertical transition energy of approximately 2.3 eV. This is the first observation of a triplet state in a compound with a pentafulvene pi-electron system. Semiempirical calculations, as well as ab initio multiconfiguration self-consistent-held calculations for fulvene using the 4-31G basis set, lead to an assignment of the observed triplet state as I B-3(2). Both 1 B-3(2) and the lowest excited singlet state I B-1(2) mainly arise from the excitation from the highest occupied molecular orbital to the lowest unoccupied molecular orbital. A singlet-triplet splitting of 1.05 eV is derived for these states. This is about 2.5 times smaller than the corresponding value in an open-chain conjugated 6 pi-system represented by 1,3,5-trans-hexatriene. The difference expresses the smaller exchange interaction between the highest occupied and lowest unoccupied molecular orbital in fulvene and related compounds. Properties of the lowest tripler state of the parent compound fulvene are calculated by use of the multiconfiguration self-consistent-held method. According to these results the fulvene rr-electron system is expected to be planar in this electronic state. The stabilization with respect to a structure twisted by 90 degrees around the exocyclic carbon-carbon bond amounts to 0.62 eV.