Abstract: The effects of long term use of Fumaria parviflora on serum concentrations of total protein, glucose, cholesterol, triglyceride, aspartate aminotransferase (AST), alanine aminotransferase (ALT) and blood urea nitrogen (BUN) were investigated. Three groups of rats (7 rats in each group) were sampled 15 and 30 days after the oral administration of 100, 200 and 300 mg kg-1 of hydroalcoholic extract of the plant and one group (7 rats) was sampled as control. There was no significant difference between treatment and control groups at day 15. At day 30, administration of 300 mg kg-1 of the extract caused a significantly higher serum concentration of AST than other groups (p<0.05). This group also have higher serum ALT than the group which received 100 mg kg-1 of the extract (p = 0.043). The rats that received 300 mg kg-1 of the extract had significantly higher serum total protein than the group which received 100 mg kg-1 of the extract (p = 0.04) and had a marginally higher total protein than the control group (p = 0.08). According to the results of the present study, it seems that long-term administration of F. parviflora extract with lower doses than that reported by other authors may cause hepatic damage.