1. A series of 62 nasal carriers of B. diphtheriae, virulent and avirulent, has been investigated.
2. Treatment by means of normal saline gargles and sniffing normal saline up both nostrils appeared to reduce the number of positive swabs by two, but the data are not quite decisive on this point.
3. With the above treatment the majority of the patients were carriers for periods of less than 9 days.
4. Two successive negative swabs were followed by positive results in 22 cases.
5. In order to recognise 99 per cent, of the carriers in a population receiving treatment with normal saline, five swabs are required from each person examined.
6. Equations are given by which the expected length of run may be calculated for other conditions.