Publisher Summary This chapter discusses the problems in the determination of manganese in biological material. In most animal species, manganese deficiency results in skeletal abnormalities, poor posture, and impaired reproduction. Symptoms include a decrease in plasma cholesterol; slowed growth of hair and nails; a reddening of the beard and hair and scaly dermatitis. The importance of contamination-free sample collection procedures and reliable determination in eliminating potentially misleading data is illustrated. Manganese is present in body fluids and tissues at very low concentrations. The determination of a small concentration of manganese in a high concentration of matrix results in spectral and chemical interferences becoming more significant, usually leading to positive errors. With these low levels, only the most sensitive analytical techniques are suitable. Two techniques used are—namely, Neutron Activation Analysis (NAA) after radiochemical separation and Graphite Furnace Atomic Absorption Spectrometry (GF-AAS). Two other techniques used are inductively-coupled plasma atomic emission spectrometry (ICP-AES) and inductively-coupled plasma mass spectrometry (ICP-MS). Preconcentration techniques using a poly (dithiocarbamate) resin are applied to the determination of manganese in urine.