A number of distinct secretory phospholipases A2 (PLA2) have been characterized in the human. Elevated group II PLA2 serum levels are associated with inflammatory diseases such as infections, septic shock, rheumatoid arthritis, multiple organ failure and acute pancreatitis. The cellular source of circulating group II PLA2 has not been defined unequivocally. The possible role of the liver as a source of circulating group II PLA2 in acute pancreatitis was studied using liver biopsies from five patients operated on for necrotizing acute pancreatitis and from two control liver samples. Reverse transcription polymerase chain reaction (RT PCR), northern hybridization and in situ hybridization were used to study the expression of group II PLA2. Immunohistochemistry was used to study the localization of the group II PLA2 protein in liver cells and time-resolved fluoroimmunoassay to measure the plasma group II PLA2 content. Expression of group II PLA2 was found in the livers of patients with acute pancreatitis by RT PCR and confirmed by northern hybridization. Group II PLA2 mRNA was localized in hepatocytes by in situ hybridization. Faint immunopositivity was found in Kupffer cells. Time-resolved fluoroimmunoassay revealed elevated concentration of group II PLA2 in plasma samples. Only low levels of expression were found in the control livers. Group II PLA2 is expressed in the livers of patients suffering from acute pancreatitis but not in the livers of patients without pancreatic disease. The current results support the idea that hepatocytes are an important source of circulating group II PLA2 in inflammatory diseases.