We characterized electroluminescent porous silicon samples made from n-substrates by their luminescence behaviour. Electroluminescence (EL) and photoluminescence (PL) spectra are compared. PL spectra have their peak at about 1.8 eV and a full width at half-maximum of 0.3 eV. EL in the same spectral region is observed for both directions of the current. The spectral distribution of the emitted light, however, depends on the direction of the current. For the investigated samples with contact layers of gold or indium tin oxide, we determined a yield of about 1 photon per 10high5 electrons crossing the sample if bulk n-Si is connected to the positive power supply. The efficiency of light emission depends on the sense of the current.