Abstract The luminescence of the following crystals is reported: RbY2F7:Gd, RbGd2F7 and KGdF4. The crystal structure of the heptafluorides is not know. It contains at least seven, and probably eight, different sites for the lanthanide ions. The vibronic lines belonging to the 6 P 7 2 → 8 S emission transition of Gd3+ are relatively intense (~ 10% of the electronic lines). At low temperatures RbGd2F7 mainly shows the Gd3+ trap emission due to energy transfer between Gd3+ ions. At higher temperatures the energy migration in the Gd3+ sublattice becomes so fast that mainly lanthanide impurity emission is present. Several aspects of this impurity emission are dealt with. The properties of KGdF4 are similar, but due to the presence of some oxygen in the tetrafluoride lattice there are also differences.