We present a combined experimental and theoretical study of the plasmon dispersion in a quasi-onedimensional conductor, the transition metal tetrachalco-halogenide (TaSe 4 ) 2 I. The dispersion relation, as measured by electron energy-loss spectroscopy in transmission, is quasilinear, which is not expected from the literature. However, we show that the data can be explained within a one-band model, which additionally allows the derivation of the conduction-band dispersion. Thus, contrary to evidence from photoemission measurements, we find no hint for singular properties caused by one dimensionality. ͓S0163-1829͑98͒07419-0͔