Phospholipase A2 (PLA2) modifications were investigated in patients with acute and chronic liver diseases, PLA2 variations were related to indices of liver function as well as to parameters of the acute phase response. Serum PLA2 activity modifications were fluorimetrically measured in 105 patients affected by acute and chronic liver diseases or extra-hepatic diseases. One-way ANOVA demonstrated a significant difference among groups (F = 4.53, P < 0.001); Bonferroni's test for pairwise comparisons showed that patients with hepatocellular carcinoma had higher mean values than subjects with benign extra-hepatic diseases (P < 0.01) and mild chronic liver disease (P < 0.05). Multiple regression analysis, performed choosing PLA2 as the dependent variable and blood urea nitrogen, C-reactive protein, alkaline phosphatase and alpha 1-fetoprotein as predictor variables was significant (multiple R = 0.7056, multiple R2 = 0.4978, F = 15.36, P = < 0.0001). The standardized regression coefficients found to be significant were those of C-reactive protein, blood urea nitrogen and alpha 1-fetoprotein. In conclusion, in patients with chronic liver disease, serum PLA2 activity increases parallel to disease severity and accompanies the expression of proteins of the acute phase response that, like PLA2 activity, increase in serum while liver synthesis declines.