A study has been made on an isolated group of children with heart disease.

All of these individuals, with one exception, were rheumatic subjects.

Many of them carried a strain of hemolytic streptococcus in the throat flora during the winter of 1934. The organism produced no detectible toxin and was not associated with respiratory disease.

Four patients contracted chicken pox during the winter months. None developed rheumatic recrudescences.

All of the individuals were in good health on March 1.

A severe epidemic of influenza began on March 22. All but six children contracted the disease. The filterable virus responsible for this outbreak was recovered.

This agent did not activate the rheumatic process. It was followed by an outbreak of streptococcus infection and appeared to facilitate its spread.

The source of these infections was not traced. They were due to a single type of hemolytic streptococcus which was a strong toxin producer. Its cultural, biochemical and serological characteristics were different from those of the carrier strain.

Of seventeen individuals proven bacteriologically to be infected with the epidemic strain, fourteen rheumatic subjects developed acute rheumatism, two rheumatic subjects and one patient with congenital heart disease escaped.

These fourteen rheumatic attacks were accompanied by a rise in antistreptolysin titer coincident with the onset of symptoms.

In four of these attacks it was possible to exclude influenza as a causative factor.

The clinical observations, the bacteriological findings and the immunological evidence indicate that this severe outbreak of rheumatic fever was caused by Streptococcus hemolyticus, which appeared to be a single strain by type.