IN a report recently issued by the Ministry of Health, a routine procedure is described for the bacteriological examination of water supplies (Reports on Public Health and Medical Subjects, No. 71. London: H.M. Stationery Office. 9d. net). Hitherto, almost every laboratory has employed its own technique, so that reports by different analysts on the same samples of water may show considerable variation and discrepancies. In a quantitative procedure like water analysis, it is especially important that all workers should employ the same methods, otherwise results, and the interpretation thereof, must vary from one laboratory to another. The procedure described in the present report, drawn up by an influential committee which included the late Sir Alexander Houston, if generally adopted, should go fair to ensure more uniformity than formerly. The Committee, while describing in detail the general procedures, allows considerable latitude for the determination of the various indexes of excretal pollution. One of the principal innovations is the substitution of agar for gelatin medium for the count at 20° C., and tables are provided by which the most probable numbers of B. coli in 100 ml. may be determined. Standards are suggested, and precise details are given for the taking of samples.