The allograft inflammatory factor-1 (AIF-1) is a 17 kDa interferon-gamma-inducible Ca(2+)-binding EF-hand protein that is encoded within the HLA class III genomic region. Three proteins are probably identical with AIF-1 termed Iba1 (ionized Ca(2+)-binding adapter), MRF-1 (microglia response factor) and daintain. Considerable but not complete sequence identity with AIF-1 has been described for IRT-1 (interferon-responsive transcript), BART-1 (balloon angioplasty-responsive transcript), and other, yet unassigned alternatively spliced variants. In this review, genomic and functional characteristics of AIF-1-related proteins are summarized and a common nomenclature is proposed.