Blood culture bottles are frequently found to be positive before colonies of the infecting organism are available for susceptibility and biochemical testing. It is current practice to perform susceptibility testing and screening biochemical testing from positive blood culture bottles and then to repeat these from colonies. This repetition means increased material and labor costs for the laboratory, and has not been demonstrated to be necessary. This study compared bottle and colony susceptibility and biochemical results to define the circumstances under which repeating the tests from colonies is really necessary. The study has been completed, and it has been found that reliable susceptibility test results can be obtained from tests set up from blood culture bottles. We no longer repeat sensitivities set up directly from blood culture bottles, but are repeating biochemical tests set up directly from blood culture bottles.