To confirm the sensitivity of the polymerase chain reaction (PCR) technique (versus blood cultures) and to gain a better understanding of the incidence of true- and false-positive results when using this technique, one hundred randomly chosen patients treated operationally because of valve defects were examined. In our studies we found that PCR techniques using universal primers complementary to the bacterial 16S rDNA showed promise as being more sensitive than conventional blood culture (BC) techniques. From the time that a blood culture is positive, conventional methods of culture and antibiotic susceptibility testing require at least 64 h for the detection of infection or colonization. Rapid identification of bacteria from blood using PCR technique accelerates the microbiological diagnosis.