A study was undertaken to evaluate the sensitivity, accuracy and practicability to a two-bottle nonradiometric blood culture system (BACTEC NR 660) with the two bottle conventional blood culture system in use in our laboratory. A total of 592 sets of four blood culture bottles were collected from adults in a twenty-week period, giving 126 positive sets. The conventional system recovered 121 isolates, whereas the BACTEC NR 660 system recovered 97 microorganism. The difference in the recovery rate was not statistically significant. Contaminant isolates were detected with greater frequency in the conventional system (p less than 0.001). Microorganism were recovered faster in one or both BACTEC NR 660 bottles than in conventional system (p less than 0.001). Our study confirms that BACTEC NR 660 system is suitable for routine detection of bacteremia.