Infrared and Raman spectra have been measured of scheelites with formula ALnW 8 O 8 , ALnMo 2 O 8 (A = Li, Na, K; Ln = La, Y), Y 2 MWO 8 M = Ge, Si), Y 2 GeMoO 8 and the zircon Y 2 SiMoO 8 in order to get information about the crystallographic order. The A + and Ln 3+ ions in the scheelites ALnW 2 O 8 and ALnMo 2 O 8 are probably ordered in layers Ln-Ln-A-A perpendicular to the c-axis. The order is short-range only. The degree of order decreases in the sequence K, Na, Li. The compounds Y 2 MWO 8 and Y 2 GeMoO 8 are not ordered, whereas the Si 4+ and Mo 6+ ions in Y 2 SiMoO 8 are ordered in alternate layers perpendicular to the c-axis. The use of vibrational spectra for the determination of crystallographic order is discussed.