Automated blood culture systems are intended to make the processing of blood cultures more efficient. This is accomplished by (1) eliminating the need for blind or terminal subcultures of bottles, (2) reducing the number of times bottles must be handled during processing, (3) standardizing and speeding detection of microbial growth, and (4) maximizing blood culture sensitivity and specificity. This article reviews three generations of automated systems that have been developed and marketed during the past 20 years and discusses their relative advantages and disadvantages.