Details are given of two simple tests for efficiency of pasteurisation. The first, test A, may be carried out completely within half an hour, and will detect any gross errors of pasteurisation technique. The second, test B, is more searching, and will reveal minor errors of technique as follows:

(a) 1½° F. below the minimum temperature for pasteurisation, or (b) heating (at 145° F.) for 20 instead of 30 min., or (c) admixture of 0·25 per cent, of raw milk with properly pasteurised milk. Taken together, the two tests form an efficient method for the laboratory diagnosis of faulty pasteurisation.