Gamma glutamyl transferase (GGT) and alkaline phosphatase (ALP) may not be sensitive indicators of hepatocellular damage in patients taking anticonvulsant drugs as raised levels may only reflect enzyme induction. Aspartate aminotransferase (AST) is a specific, but relatively insensitive marker of liver damage and has a poor correlation with liver histology. Serum F protein is found in high concentration in the liver and levels are not influenced by enzyme induction. We measured serum F protein levels in patients taking carbamazepine (CBZ) and phenytoin (PHT) as monotherapy and in patients receiving multiple drugs. We compared the results with patients taking sodium valproate (VPA). Serum F protein levels were elevated in 6%, 22% and 13% of patients receiving CBZ, PHT and VPA, respectively. Raised GGT levels were reported for both the CBZ (26%) and PHT (78%) groups. Raised ALP levels were observed in 16%, 25% and 4% of the CBZ, PHT and VPA groups, respectively. Raised levels of serum F protein in the VPA group and the absence of any associated increases in either GGT or AST may further support the suggestion that serum F protein is an indicator of hepatocellular dysfunction associated with anticonvulsant therapy. However, further correlation with liver histology is required.