The exposure of mice to static magnetic fields (MF) of different strengths (1000-4000 G) for 10 min was studied. The effects of these magnetic fields on the function of haemoglobin (Hb), and its conformational stability, auto-oxidation kinetics, bioenergetics and viscosity, and those of different Hb derivatives were investigated. The fractions and concentrations of the inactive Hb pigments (such as methaemoglobin, carboxyhaemoglobin and sulfohaemoglobin) and the active Hb (in the HbO2 form) were determined using a newly developed multi-component spectrophotometric method. The direct effect of magnetic fields of relatively high strengths (3500 and 4000 G) led to different Hb conformations, accompanied by changes in intermolecular interactions represented by the slope of the eta sp/C = F(C) lines and Huggins' constant K', while no measurable change in the intrinsic viscosity [eta] of Hb was observed. These results indicate a lack of changes in the dimensions and shape of the Hb molecule. Study of the kinetics of oxyhaemoglobin auto-oxidation revealed decreases in the auto-oxidation reaction rate of 2-5.9% and 10-17%, under the effect of static MFs of strengths 1000-2500 G and 3500-4000 G, respectively.