Asymptomatic bacterascites is defined as the presence of bacteria in ascitic fluid without clinical features of peritonitis or increased ascitic fluid polymorphonuclear cells. Asymptomatic bacterascites is a controversial entity, and little information is available regarding its spontaneous evolution. Clinical features, bacteriological data and outcome in 22 cirrhotic patients with asymptomatic bacterascites are reported and are compared with those of a group of 36 cirrhotic patients with spontaneous bacterial peritonitis. Eleven patients had gram-negative bacteria and 11 had one gram-positive bacteria. Only in three patients (13.6%) did peritonitis develop. Twelve patients received no antibiotic therapy, and in none did peritonitis develop. At 1 month, 27% of patients with asymptomatic bacterascites had died. Patients with asymptomatic bacterascites had less-severe liver disease; they more frequently had gram-positive bacteria in ascitic fluid and had a lower 1-mo mortality rate than did patients with spontaneous bacterial peritonitis. We conclude that asymptomatic bacterascites is usually the transient residence of bacteria in ascitic fluid. Peritonitis rarely develops in patients with asymptomatic bacterascites and, in most of them, antibiotic therapy is not required.