An investigation has been carried out over a period of 7 years of a series of eighty-one patients who first presented in 1951–52 with staphylococcal lesions. In seventy-two oases (89%) the infection was limited to a single, short episode of infection without recurrence. But nine patients (11%) developed recurrent lesions throughout the period. In these patients, from a comparison of the phage types isolated from successive infections, it was inferred that the organism had persisted in the body for over 6 years in two cases, for 4–5 years in five cases and for 1·3 years in three cases.

Nasal carriage also persisted for over 6 years in two cases and for 3–5 years in three cases.

In two cases, chronic skin carriage occurred in the absence of nasal carriage. There was persistence of staphylococci for 3 and 5 years in these cases, and the use of a special technique revealed that carriage in the deeper layers of the skin was particularly important.

The frequency distribution of phage patterns isolated in recurrent cases reflected the high incidence of Group II strains at the time when the strains were first acquired. New infections which arose in 1957–58 no longer showed this preponderance of Group II strains, as only eleven (28%) of thirty-eight new infections were caused by this group.

The bacteriological examinations were mostly carried out by the Central Public Health Laboratory, Colindale, and I wish to express my gratitude to Dr R. E. O. Williams of the Staphylococcal Reference Laboratory, for his assistance in this work. I am also grateful for the laboratory facilities afforded me by Dr Ridley at the Hospital for Tropical Diseases for the performance of the skin carriage testing.