[en] Two new aluminum spectra have been observed with EPR in irradiated vitreous silica. Under electron irradiation at 4⁰K, the low temperature (LT) Al spectrum is produced, and it changes into the high temperature (HT) spectrum upon annealing between 230 and 330⁰K. The HT Al spectrum is also produced directly upon irradiation at room temperature. Each spectrum is characterized by six well resolved ²⁷Al (I = 5/2) hyperfine lines (A/sub isotropic/(LT) = 0.00330 cm^-1 and A/sub isotropic/(HT) = 0.0410 cm^-1). These spectra are the most intense in type I and II vitreous silicas which contain Al as a natural impurity. The difference in these spectra may reflect the presence of a neighboring charge compensator, such as an alkali, which becomes mobile at approximately equal to 270⁰K. It is possible that these spectra correspond to Al E₁'-type centers with the unpaired electron strongly localized on a substitutional Al which is bonded to only three oxygen atoms