Yb3+ excitation in the near-infrared around 1 mum leads to green Mn2+.4T1 -->(6)A(1) luminescence in CaZnF4:Mn2+; Yb3+, ZwSiO(4):Mn2+; Yb3+ and SrZnCl4:Mn2+; Yb3+ at 15 K. In the former two compounds the green upconversion (UC) luminescence is visible by eye up to room temperature. In Cs3MnBr5:Mn2+; Yb3+ no UC luminescence is observed. The UC mechanism consists of a sequence of ground-state absorption and excited-state absorption steps. The UC efficiency at 15 K is of the order of 1% for laser excitation with 130 mW (f = 53 mm focusing lens). (C) 2004 Elsevier B.V. All rights reserved.