We determined the serum levels of leptin in 96 pregnant women with body mass index between 20 to 30, 30 normal (NP), 26 with mild preeclampsia (MPE), 27 with severe preeclampsia (SPE), 6 with chronic hypertension plus preeclampsia (CHT+PE) and 7 with chronic hypertension (CHT). A significant (p < 0.01) decrease in leptin levels was observed in the SPE group when compared with the NP group. On the contrary, significant (p < 0.05) increases were observed in the CHT and CHT+PE groups when compared with the NP group. Leptin levels were significantly higher in the MPE (p < 0.001), CHT (p < 0.01) and CHT+PE (p < 0.5) groups when compared with the SPE. No significant differences were observed in the CHT group when compared with CHT+PE. Moreover, a positive correlation was encountered (r = 0.6, p < 0.001) between platelet number and leptin levels for all the patients with preeclampsia. These results suggest that leptin levels may be useful metabolic parameter in different types of hypertension during pregnancy.