Pro-inflammatory cytokines are implicated in the cascade of events leading to human parturition. We hypothesise that cytokines induce changes in key calcium homeostatic mechanisms, which in turn augments myometrial contractility prior to labour. We have recently demonstrated using fura-2 and fluorescent digital imaging that capacitative calcium entry (CCE) is present in primary cultured human myometrial smooth muscle (HMSM) cells, and is amplified by treatment with interleukin-1β (Tribe et al., 2003). The aim of the present study was to characterize the channel currents associated with CCE in these cells. HMSM cells were isolated from myometrial biopsies obtained from women undergoing caesarean section at term (non-labour, 38-41 weeks gestation). Cells were maintained in primary culture until confluence was reached (in DMEM with 5% fetal calf serum) and then either serum-deprived (0.5% fetal calf serum) for 48 h (controls) or serum-deprived for 24 h and treated with IL-1β (10 ng/ml) for a further 24 h. Treated and control cells were isolated using a cell dissociation solution containing EDTA and CCE currents recorded using the whole cell voltage clamp technique. The membrane potential was clamped at −70mV and currents activated by cyclopiazonic acid and thapsigargin were continuously recorded using a CsCl2 (mM 135 CsCl2, 10 HEPES, 3ATP, 1MgCl2, 5TEA, 10 EGTA, 2CaCl2, 14-AP) pipette solution. Neither K+ nor L-type calcium channels were active under these conditions. In control HMSM cells, inhibition of SERCA pumps activated a noisy inward current at −70mV in 25% of cells, which was abolished by replacing extracellular sodium with NMDG. In IL-1β treated cultured human myometrial smooth muscle cells, on the other hand, the current was detected in the majority of cells examined and Na+ removal led to only a 50% decrease in current amplitude instead of a complete block. Lanthanum rapidly inhibited this current in both control and IL-1β-treated cells. These results suggest that IL-1β alters the functional expression of CCE currents to promote calcium influx in HMSM cells, and that this pathway may contribute to the preparation of the uterus for labour.