FAM19A4 (family with sequence similarity 19 member A4; also TAFA4) is a classical secretory protein expressed mainly in the central nervous system and upregulated significantly in lipopolysaccharide (LPS)-stimulated monocytes and macrophages. It is a novel cytokine ligand of formyl peptide receptor 1 (FPR1), showing chemotactic activities on macrophages and promoting the phagocytosis capacity and the release of reactive oxygen species (ROS) by macrophages upon zymosan stimulation. Based on the same detection principle as enzyme-linked immunosorbent assay (ELISA), we developed a sandwich immunoassay for quantitative detection of FAM19A4 in biological fluids by flow cytometry, with latex beads as solid carrier. The method showed good performance in a wide range of 39-10,000 pg/mL and possessed excellent specificity, good precision, and favorable recovery in several different matrices. Native FAM19A4 secreted by phorblo 12-myristate 13-acetate (PMA) and LPS stimulated THP-1 cells could also be detected by this method. This method will be much helpful to FAM19A4 studies. (C) 2017, The Society for Biotechnology, Japan. All rights reserved.