OBJECTIVE: We investigated whether maternally inherited mitochondrial deoxyribonucleic acid mutations could be associated with preeclampsia because mendelian models fail to explain all the aspects of inheritance in preeclampsia. STUDY DESIGN: In two families with a high occurrence of preeclampsia and eclampsia the 22 mitochondrial transfer ribonucleic acid genes were sequenced in eight and three women, respectively. RESULTS: An A-to-G mutation in transfer ribonucleic acid^leu[UUR] at nucleotide 3243 was found in one family, and in the other there was an A-to-G mutation at nucleotide 12308 in transfer ribonucleic acid^leu[CUN]. Mutations of mitochondrial transfer ribonucleic acid genes are generally considered to have systemic consequences, which might explain the multiorgan involvement seen in preeclampsia. CONCLUSION: We report for the first time mutations in mitochondrial transfer ribonucleic acid genes in two families with a high occurrence of preeclampsia and eclampsia. Mitochondrial dysfunction caused by point mutations of mitochondrial deoxyribonucleic acid is maternally inherited, but in the case of mutations of nuclear genes mitochondrial dysfunction can be inherited as an autosomal recessive or dominant trait. (AM J OBSTET GYNECOL 1996;174:1626-30.)