Tests for the presence of Coxsackie virus were carried out with specimens of feces and swabbings of the nasopharynx from 20 infants and children suspected of having poliomyelitis who were admitted to a hospital during the summer of 1949 in New York City. Both Coxsackie virus and poliomyelitis virus were recovered from feces collected during the course of illness from each of two children with paralysis. The strains of Coxsackie virus which were isolated from both of these patients were found to be serologically related to Dalldorf's Type 1 Coxsackie virus. The Coxsackie and poliomyelitis viruses which were isolated from one of these patients were found not to be immunologically related to each other. Tests with specimens of serum from both patients showed that one but not the other developed, during convalescence, an increase in the capacity to neutralize the strains of Coxsackie virus which were isolated from them.