ASAP1(I67T.Q397R) is a genetically encoded fluorescent voltage indicator. It was generated by introducing amino acid substitutions I67T and Q397R into ASAP1. ASAP1(I67T.Q397R) shows larger changes in fluorescence to depolarization and smaller fluorescence changes to hyperpolarization compared to ASAP2f (FBrf0232743). For detailed kinetic and spectral properties and a comparison of ASAP1(I67T.Q397R) with other fluorescent voltage indicators, see FBrf0232743.