Polarized Raman spectra of single crystals of barium copper formate [Ba2Cu(HCOO)6] at room temperature were recorded and analysed. The spectra were obtained for geometries allowing the observation of A(TO) and BTO + LO) species. The assignment of the fundamental modes was performed on the basis of formate group vibrations and correlations with previous data reported for other formate crystals. The observation of four separate wavenumbers for all internal modes of formate ion is indicative of four crystallographically non-equivalent formate ions in the unit cell. Copyright © 2000 John Wiley & Sons, Ltd.