Pre-eclampsia is an endothelial disorder and TNF-α has fundamental effects on endothelial cells by several means, including altering the balance between oxidant and anti-oxidant, changing the pattern of prostaglandin production and affecting expression of several cell surface components. To determine whether TNF-α mRNA expression is increased in pre-eclamptic patients, leucocytes from pre-eclamptic patients, normal pregnant women and normal non-pregnant women were studied for TNF-α expression using a quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) method. Using a model of 373A ABI Sequencer, TNF-α gene polymorphism was also analysed by GENESCAN and Genotyper software in order to explain the mechanism of abnormal TNF-α expression. Our results show that TNF-α mRNA expression is significantly elevated in pre-eclamptic patients compared with the other two control groups. The high expression of TNF-α may be associated with the TNF1 allele, whose frequency is markedly increased in pre-eclamptic patients. These observations are consistent with a major role for TNF-α in mediating endothelial disturbances, and suggest a key role for TNF-α in the development of pre-eclampsia.