Fast-GCaMP-EF15 is a genetically encoded fluorescent Ca[2+] indicator with fast kinetics. It consists of a calmodulin-binding peptide, a circularly permuted green fluorescent protein and calmodulin. Fast-GCaMP-EF15 was derived by mutagenesis of GCaMP3, containing in addition the mutations D431N, D433N and D435N, which are in the fourth EF-hand loop of the C-terminal Ca[2+]-binding domain (FBrf0222168). For detailed kinetic and spectral properties, see FBrf0222168.