The article compares the ability of detection and detection times (TTD) of aerobic bacteria in the BacT/Alert FA, BacT/Alert SA, Bactec Plus Aerobic/F and Bactec Standard Aerobic/F bottles. Compared bottles were inoculated at the same time with the identical suspension of bacterial strain. All bottles detected bacterial pathogens even in the case of very low number of inoculated bacteria. The differences of TTD were detected between the bottles of compared hemocultivation systems. Bactec Plus Aerobic/F system is faster in the detection of the members of family Enterobacteriaceae at 1-3 hours, BacT/Aert FA system is faster in the detection of coagulase-negative staphylococci. Most difference was detected at Pseudomanas stutzeri, where the detection in BacT/Alert FA bottles was at 15 hours faster in opposite of Bactec Plus Aerobic/F bottles. In the bottles without sorbent Staphylococcus aureus and Streptococcus sanqui were detected faster in the system Bactec Standard Aerobic/F. The bottles BacT/Alert SA detected faster skin corynebacteria. Detected differences have not a practical importance for the blood stream infection diagnostics.