Results are given of the typing (by biochemical fermentation tests) of 290 strains of Bact. paratyphosum B isolated during an epidemic in the north of Scotland. Of these strains 283 were of type R3I1. Seventy-four strains isolated in or around Edinburgh later in the same year, and 107 strains from three patients were also typed. Some variation (2·4 % in the north and 4 % in Edinburgh) was observed, but, in general, typing by the fermentation of rhamnose and inosite is of epidemiological significance.

I am indebted to Dr Kirkpatrick for supplying strains of Bact. paratyphosum B and providing access to the necessary records, to Dr Seiler for epidemiological notes on the Edinburgh cases, and to Prof. Mackie for his valuable advice and encouragement.