A comparison of the burdening effects on the reticulo-endothelial system (RES) by soybean oil emulsions with two different emulsifiers [soybean lecithin (SOB) and egg lecithin (EGG)] or by a perfluorochemical emulsion (Fluosol-DAR, PFC) was performed using a magnetometric method. This method is based on measuring the relaxation of injected iron oxide (gamma-Fe2O3) above the liver after magnetization in a strong external magnetic field. Three different methods of evaluation of the data were chosen. First, according to the conventional monoexponential function, second, according to a monoexponential function with a constant, and third, using the ratio of the initial dynamic to total magnetic field strength. In contrast to SOB and EGG, the PFC emulsion which was used depressed the RES-capacity to less than 31% of the control values (p less than 0.001). Following the administration of SOB the phagosomal motion was significantly lowered after 6 h (p less than 0.01) and 1-2 days (p less than 0.05); thereafter no significant difference of the relaxation constants remained as compared to the control group. The fatty emulsion with egg lecithin showed no significant lowering of the RES-capacity during the entire observation period (p greater than 0.05). Our results indicate that the RES-capacity is diminished not only by a PFC emulsion, but also temporarily by a soybean lecithin emulsion, though not by an egg lecithin emulsion, when given in the same dosages.