Vascular smooth muscle cells (VSMCs) express a large repertoire of ion channels and membrane receptors, which are a key determinant of the electrical and contractile responses of the cells. Contractile activity of VSMCs is triggered by Ca²⁺ influx through voltage-activated Ca²⁺ channels, and because of this voltage dependence, membrane potential is the primary determinant of VSM tone. K channels, as key players in controlling membrane potential, may have an important role in dedifferentiation and proliferation processes in VSMCs, and it is becoming clear that their contribution to cell proliferation is a complex modulatory activity that only certain K channels at specific times and locations can perform. This fact, together with the broad diversity of functional K currents among different vascular beds, that results largely for the great diversity of K channels expressed, has ravelled the analysis of the role of K channels on VSMCs proliferation. Among the different types of K channels found in VSMCs, voltage-dependent (Kv) and large-conductance, calcium activated (BKCa) K channels are present in virtually all vascular myocytes and have been shown to strongly influence contractile responses. In this study we characterised the expression profile and the functional involvement of Kv channels in VSMCs from human uterine artery in contractile and proliferating phenotype, in order to evaluate their functional role in VSMCs from human resistance arteries and their possible contribution to the phenotypic modulation of the cells. Uterine arteries were obtained from women subjected to hysterectomy. Enzymatic dispersion of small pieces of the muscular layer of these arteries provide VSMCs in contractile phenotype, while proliferating VSMCs were obtained from explants of uterine arteries kept in culture for several passages. We found that the proliferation process in uterine artery leads to a decreased expression of BKCa channels without a significant change in the outward current density, implying an increase in the proportion of Kv currents in dedifferentiated VSMCs. The molecular identification of the functional Kv channels in both preparations shows that while Kv1 members are the main contributors to the Kv currents in contractile VSMCs, Kv3.4 expression is up-regulated under proliferating conditions and represents the largest proportion of the Kv current in dedifferentiated VSMCs. This functional characterization was supported, with slight discrepancies, by the determination of the expression levels of the corresponding mRNAs by quantitative RT-PCR. Finally, we demonstrate a direct relationship between Kv3.4 channel function and VSMCs proliferation rate, showing that selective blockade of Kv3.4 channels leads to a decrease in the number of VSMCs without increased apoptosis.