1. In the absence of the epidemic prevalence of the dysenteries over a period of 30 months it is found that cases of the various forms of dysentery as occurring in Aberdeen have been in the proportion of 1 amoebic, to 3 Flexner, to 6 Sonne dysenteries, and it is concluded that B. dysenteriae Sonne is the most frequent cause of dysenteric outbreaks in Aberdeen in non-epidemic times.2. A description of the clinical and bacteriological features of Sonne dysentery is submitted.3. Preliminary experiments, undertaken with a view to ascertaining whether B. dysenteriae Sonne produces a true exo-toxin, are described.