The main infrared absorption band of the antenna of the purple bacterium Rps. uiridis is investigated using low-temperature absorption and site-selected fluorescence spectroscopy. Low-temperature absorption spectra show that at least three bands are present in the near-infrared. Gaussian fits indicate that the maxima are located around 1015, 1030 and 1045 run. Fluorescence measurements using narrow-band laser excitation in the red flank of the absorption band show that the emission is highly polarized ( p > 0.3). This was found for membranes and (isolated) core complexes. In isolated core complexes, the polarization of the emission increases smoothly as a function of the excitation wavelength, starting in the center of the absorption band, whereas in membranes the increase is abrupt and occurs in the extreme red edge. These results differ significantly from similar measurements performed on core light-harvesting complexes from Rhodobacter sphaeroides [Van Mourik, F., Visschers, R.W., Van Grondelle, R. (1992) Energy transfer and aggregate size effect in the inhomogeneously broadened core light-harvesting complex of Rhodobacter sphaeroides, Chem. Phys. Lett. 193, 1–7] and cannot be interpreted by assuming a single inhomogeneously broadened pool of antenna pigments. Moreover, the low-temperature absorption spectrum gives clear evidence for a long-wavelength spectral form. Therefore, it is concluded that the antenna is heterogeneous, with a minor long-wavelength spectral form (131045). The fluorescence measurements show that this 131045 band is inhomogeneously broadened.