Bacterial translocation is currently considered the main pathogenic mechanism leading to spontaneous bacterial peritonitis in patients with advanced cirrhosis and ascites. However, to the authors' knowledge there is no information regarding the characteristics of this process in humans. The goals of the current study were to pursue partially identified bacterial DNA in blood (what the authors consider molecular evidence of bacterial translocation) through its relative quantification in a 72-hour study period by using real-time polymerase chain reaction (PCR). A consecutive series of 17 patients with advanced cirrhosis and culture-negative, nonneutrocytic ascites were studied. Therapeutic paracentesis was performed at the time of admission, and blood samples were obtained at baseline and every 8 hours in a 3-day period. Bacterial DNA was detected by a PCR-based method, relatively quantified by real-time PCR, and identified by automated nucleotide sequencing. Seven of 17 patients demonstrated the simultaneous presence of bacterial DNA in blood and ascitic fluid at the time of admission. After therapeutic paracentesis was performed, bacterial DNA persisted in the blood for a minimum of 24 hours, and was reported to last as long as 72 hours in some patients. In addition, different patterns of bacterial DNA appearance and clearance from the blood were identified. The nucleotide sequencing process demonstrated that bacteria detected in the first sample were identical to those noted in subsequent detections over time. In conclusion, bacterial translocation is a single-species, dynamic process that appears to develop in a subgroup of patients with advanced cirrhosis.