Abstract: Transferrin, haptoglobin, IgG, IgA, IgM and orosomucoid in plasma, and albumin in urine were determined by flow injection analysis on a FIA Star (Tecator) system. Samples were diluted up to 200-fold with carrier solution and a 40 µL portion was injected into carrier solution of 0.05 M phosphate - 0.1 M NaCl buffer (pH 7.4) containing 4 or 7% of polyethylene glycol and mixed with antibody solution; detection was at 405 nm. The results are presented for each protein; the method is not suitable for IgG, IgA and IgM and can be used for orosomucoid if a kinetic setup is applied.