Abstract: An antimicrobial composition for the preservation of milk samples required for analysis. The composition comprises 2-bromo-2-nitropropane-1,3-diol and natamycin, in effective amounts to prevent spoilage of the milk for a period of at least 5 to 10 days. The amount of 2-bromo-2-nitropropane-1,3-diol for a 50 ml milk sample is preferably 6-12 mg and the amount of natamycin is preferably 0.3-0.6 mg. The composition is preferably employed in the form of a tablet containing a suitable filler and usually other ingredients. In a method of preserving milk samples, the 2-bromo-2-nitropropane-1,3-diol and natamycin may be added separately or simultaneously (e.g. in admixture). The composition and method provide a way of preserving milk samples without the health problems associated with conventional preservatives such as dichromates and without the need to refrigerate the milk.