Streptococcus diacetilactis, isolated from spontaneously soured potato mash, was first described by Matuszewski, Pijanowski and Supińska in 1936(3). Its essential features included the production of large amounts of lactic acid and volatile products (including diacetyl), and it differed from the ‘lactis-cremoris’ group primarily in the production of carbon dioxide in milk, the utilization of citrate and in its vegetable origin. More recently, in his investigation of certain diacetyl-producing and citric acid-fermenting streptococci from milk and from starter cultures, Swartling(5) showed that strains which resembled closely the Str. diacetilactis of Matuszewski et al. belonged to serological group N. In an addendum to his paper, Swartling states that this observation has been confirmed by me with a freshly isolated strain of Str. diacetilactis (no. 2) received from Prof. Pijanowski and Dr Supińska the purpose of this Note is to record the experimental evidence for that statement.