Spermidine/spermine N1-acetyltransferase (SSAT) is a catabolic regulator of polyamines, ubiquitous molecules essential for cell proliferation and differentiation. Anti-SSAT antibodies (monoclonal antibodies [mAbs]) of high titer were prepared by immunizing BALB/c mice with multifocal intradermal injections and by fusing high-titer antibody-producing spleen cells with myeloma cells of SP2/0 origin. Four mAbs were selected for further characterization as classes and subclasses. Antibodies were produced by these three clones with high affinities ranging from 10(9) to 10(11) M(-1). These clones were found to be of the immunoglobulin IgG1 subclass with kappa light chain. They could recognize SSAT as determined by Western blot and immunohistochemistry. The specificity of one clone, 4H6, was studied by using the small interfering RNA (siRNA) on SSAT. 4H6 was also compared with the commercial antibody. The produced mAbs will be a useful tool for further investigation of SSAT functions in organisms.