OBJECTIVE To compare the performance of the Sentinel blood culture system with two other systems for the recovery of streptococci and anaerobes. METHODS Blood cultures were taken from 55 patients one to two minutes after dental extraction. The samples were tested by the radiometric Bactec 460; the Isolator 10, which works by lysis centrifugation; and Sentinel, a fully automated system, which detects bacterial growth by changes in the voltage between two electrodes in the media. Positive samples were subcultured and streptococci and anaerobes were further identified. Terminal subcultures were performed on all negative samples. RESULTS Sentinel was comparable with Bactec, with Sentinel recovering 20 streptococci and 14 anaerobes; Bactec isolated 26 streptococci and 15 anaerobes. The recovery of Streptococcus sanguis was significantly better from Bactec than Sentinel. The Isolator 10 recovered significantly fewer streptococci and anaerobes than either Bactec or Sentinel. Sentinel was noticeably quicker in detecting anaerobes than Bactec 460. However, there was no comparable difference with streptococci. Contaminants were recovered from 10% of Isolator 10, 2.7% of Bactec, and 7.2% of Sentinel bottles. CONCLUSIONS Sentinel and Bactec 460 were broadly comparable in the detection of viridans streptococci and oral anaerobes, and both systems were significantly better than the Isolator 10. However, the prototype Sentinel, was significantly poorer than Bactec for the recovery of S sanguis.