A fluorescence polarization immunoassay (FPIA) based on a monoclonal antibody for the determination of sulfamera (SMR) was developed. The fluorescein-labeled SMR and sulfamethazine (SMZ) were synthesized and purified by thin layer chromatography (TLC). The optimized SMR FPIA had a dynamic range from 5.4 to 218.8 ng x mL(-1) with IC50 value of 23.4 ng x mL(-1) and a detection limit of 2.3 ng x mL(-1). The specificity of the FPIA for SMR was investigated using other 16 sulfonamides and the cross-reactivity for SMR, SMZ and sulfadiazine (SDZ) was 100%, 25% and 8.6%, respectively.