Maillard reaction products (MRP) were obtained by refluxing solutions containing either arginine and xylose (AX) or histidine and glucose (HG). The solutions were tested either unfractionated or partly purified by dialysis through a Spectra/Por (R)-6 membrane with a molecular weight cutoff at 1000. The bacteria tested were both pathogenic and spoilage bacteria frequently found in food. The effects of the AX and HG added were assessed on the basis of the growth curves and the MIC (minimum inhibitory concentration) values recorded. The MIC values obtained show that the inhibitory effect of MRP is dependent on the type of MRP and type of bacteria used. As can be seen from the growth curves, the lag phase of the growth was prolonged with increased concentrations of MRP. The results of the dialysis show that the high molecular weight fraction (Mr ?1000) was more inhibitory than the low molecular weight fraction (Mr ?1000) when tested with Bacillus subtilis, Escherichia coli, and Staphylococcus aureus. The MRP used in this study have in other studies been shown to possess a high antioxidative effect. © 1983 American Chemical Society.