Luminescence from stain-etched and electrochemically etched germanium samples was observed in the blue part of the visible spectrum. Although it is weaker than the luminescence of porous silicon, its origin is of scientific interest as a parallel to the luminescence of porous silicon. Stain-etched germanium was studied in more detail. Under visible laser excitation the luminescence band is located around 525 nm. Another luminescence band around 400 nm is observed with UV excitation. The luminescence lifetime in the UV-excited band is of the order of 1 ms, compared with about 100 ns in the band excited in the visible. The luminescence intensity either passes through a maximum or slowly decreases as the temperature is increased from 8 to 300 K. This behaviour is similar to that observed in porous silicon. The IR spectra of stain-etched Ge show the presence of GeO2, -OH groups and water. In the Raman spectra the unmistakable bands of trigonal crystal GeO2 are observed. A band at 760 cm(-1) in the Raman spectra and 752 cm(-1) in the IR spectra could be assigned to substoichiometric regions and oxygen- vacancy complexes in GeO2. The chemical composition of the samples is characterized by X-ray photoelectron spectroscopy (XPS) and secondary ion mass spectrometry ( SIMS). The XP spectra give evidence for GeO2 and GeO. SIMS data show the presence of both hydrogen and -OH groups. On the basis of these data we propose that the luminescence of stain-etched and electrochemically etched germanium is due to defects in GeO2.