Abstract At 300 K the Eu 2+ ion luminesces efficiently in SrB 4 O 7 , and to a lesser extent in SrB 6 O 10 and Sr 3 B 2 O 6 . In the last compound the lowest 4f-5d absorption band is at extremely low energy for Eu 2+ . Due to this and a large Stokes shift, the Eu 2+ emission band has its maximum at 590 nm. From a comparison with the luminescence of Ce 3+ and Pb 2+ in this lattice it is concluded that a strong non-cubic crystal field splits the 5d excited state, causing the lowest f-d absorption transition to be at a low energy position. In SrB 2 O 4 and Sr 2 B 2 O 5 , only Eu 3+ was found. An explanation for this is proposed on the basis of a charge-compensation mechanism for Eu 3+ ; the luminescence of this ion is discussed as well.