The excitation of arsenic-atom spectral lines in the collisions of slow electrons with As[sub 4] molecules has been investigated. We used the extended-crossing-beams method and recorded the optical signal from the intersection region. The recorded lines are in the 213--550 nm spectral region. We also measured the optical excitation functions (OEF) in the range of electron energies 0--100 eV. The largest excitation cross sections belong to transitions from the 5[ital s] [sup 2][ital P] and 5[ital s] [sup 4][ital P] levels. A complex structure of the OEF indicated that the contribution of different excitation channels varies with the increase of electron energy. The measured onset energies show that in the near-threshold region there occurs a reaction [ital e]+As[sub 4]=As[sup *]+As[sub 3]+[ital e].