1. The results of an investigation into the clinical, epidemiological and bacteriological features of impetigo contagiosa, with special reference to the type identification of staphylococci and streptococci, are reported and discussed.
2. Of 106 impetigo cases studied, Staphylococcus aureus was isolated alone from 86 lesions (81 %), Streptococcus pyogenes alone from 6 (5·6 %), and a mixed growth of Staph. aureus and haemolytic streptococci in 14 instances (13·2 %).
3. Of the 100 strains of Staph. aureus isolated from impetigo lesions, 63 were identical in phage type (‘type 71’), and a further 17 were closely related (‘weak 71’).
4. Only one representative of ‘type 71’, and 9 of ‘weak 71’, were obtained from 164 strains of Staph. aureus from 200 persons in three control groups.
5. Of 90 strains of Staph. aureus from impetigo lesions, 64 (71 %) were resistant to penicillin. Of these penicillin-resistant strains, 54 (84 %) were of ‘type 71’, or close variants.
6. Strep, pyogenes was probably causative in at least 6 of the 18 patients yielding this organism from lesions; it was presumed to be a secondary invader in the remainder.
7. It is doubtful if nasal carriage is of importance in the epidemiology of impetigo.
8. It is concluded that there is a specific ‘type’ of staphylococcus associated with this form of impetigo.