The aim of this study was to investigate lipid profile, paraoxonase 1 (PON1) activity, and oxidative stress status in the serum of hyperemesis gravidarum (HG) patients. Thirty-six HG cases and 36 normal pregnants were included in the study. Serum total cholesterol (TC), triglyceride (TG), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), apoproteins A1 (apo A1) and B (apo B), malondialdehyde (MDA), and total antioxidant activity (TAO) values and PON1 and arylesterase activities were determined. Although serum TC, TG, LDL-C, and apo B levels were not different among; the groups (P>0.05), HDL-C (P=0.01) and apo A1 (P=0.007) levels were lower in HG patients than in normal pregnants. HG group had significantly lower serum PON1 (P=0.03) and arylesterase activities (P=0.03) compared with the control group. Additionally, mean TAO values were lower (P=0.01) and MDA levels were higher (P=0.02) in HG group than in the healthy pregnants. A significant negative correlation between PON1 and MDA was found in HG group (r=-0.33, P<0.05). The findings of this study have revealed that HG may be one of the conditions in which oxidant and antioxidant balance is impaired.