Aromatase CYP19 catalyzes the synthesis of estrogen from androgens in a tissue-specific manner. This enzyme is present in several tissues, including gonads, brain and fatty tissue. More recently, its presence has been described in vessels. Here, we describe the expression of aromatase in human uterine artery and compare its expression with that found in arteries of estrogen-dependent uterine leiomyomata from women. To do this, we employed immunohystochemical and in situ hybridization techniques. We used, a polyclonal antibody raised against the carboxyl terminus of aromatase (ARO) and RNAm probes, of the exon 1 of ARO. We found an increased immunoreactivity of ARO in uterine arteries of patients with leiomyoma as compared with control group. Probe showing positive signal in skin fibroblasts (1b), showed positive hybridization signal in normal artery, while probes with positive signal in placenta (1a), ovary (1c) and testis (1d) were over-expressed in arteries of leiomyomas.