Summary This series of publications is concerned with the effects upon soil organisms and the performance thereof of one and several applications of a total of thirty-five herbicides, with the first and second communications reporting the results of laboratory experiments conducted in an effort to determine the side effects on soil bacteria and fungi of eleven herbicidal agents after one application in two dosages to sand and loam as well as the dehydrogenase activity and formation of carbon dioxide. It has been found that where the quantities recommended by the manufacturer were used only two herbicides caused depression of one of the two groups of organisms, while four herbicides produced short-time stimulation. Quantities ten times higher than those recommended by the manufacturer resulted in bacteria being stimulated by eight herbicides and in fungi being stimulated and inhibited by three and four herbicides, respectively.