Blood cultures are often essential in the diagnosis and prognosis of disease. Frequently, however, the results obtained are difficult to interpret and correlate with the clinical state of the patient. Limitations and confusions resulting may be attributable to (1) contamination due to faulty technique in the drawing of blood or in laboratory procedures, (2) preconceived ideas of bacterial "nonpathogenicity," and (3) variations in techniques of blood culture.Bacteria can be recovered from the blood stream during physiological states and under all pathological conditions from minimal local infections to septicemias. The significance of an organism recovered from the blood stream lies in its meeting certain basic criteria. This study was made in an attempt to correlate the clinical status and the laboratory findings in patients who have had blood drawn for cultures. Certain criteria to facilitate this correlation were established.Arnold 1 experimentally produced frank bacteremia in dogs by introducing a highly acid chyme into the small intestine from the stomach. This resulted in increased permeability of the wall of the small intestine to bacteria. Arnold further demonstrated that certain physiological alterations in the body, such as adaptations to extremes of temperature, whether artificially induced or from dis¬ ease, may result in bacteremia. Cirrincione and Francona,2 also working on dogs, were able to confirm Arnold's findings.Reith and Squier3 reported a study of 293 subjects, of whom 278 were male, who had blood drawn for culture at random intervals while they were performing their usual daily occupations. All were subjected to a thorough physical examination, including dental x-rays. Bacterial