Oxytocin-induced release of Ca ions from sarcoplasmic reticulum (SR) and sensitisation of contractile proteins to Ca mediate the oxytocin-induced potentiation of myometrial contractions. Solitary transients and sustained oscillations of cytoplasmic Ca in response to oxytocin have been previously described, respectively, in freshly isolated and cultured human myometrial cells [1, 2]. In the present study, we employed the thin myometrial slices technique recently developed in our laboratory to investigate the tissue-level effects of oxytocin on human myometrium. Myometrial biopsies were taken from patients undergoing Caesarean section with informed written consent and approval from the Local Ethics Committee (REC-05/Q2802/107). Ca signalling events were recorded from Fluo-4 loaded slices using a Zeiss LSM 510 META confocal microscope at 1 and 4 frames/s. Isometric force was measured in parallel experiments using standard organ bath. Application of nifedipine (1 μM) to slices exhibiting phasic contractions led to immediate abolition of spontaneous activity. Subsequent addition of 100nM oxytocin produced an initial, transient rise in force followed by high frequency oscillations in >50% of preparations. Confocal microscopy of myometrial slices subjected to identical experimental protocol revealed asynchronous oscillations in cytoplasmic Ca at the beginning of oxytocin application which tended to synchronise at later stage of oxytocin application. We quantified the synchronicity of oscillations as standard deviation of time delays between the start of oxytocin application and the first peak of Ca in different cells within the field of view. The standard deviation was 33.62 s at the beginning, decreasing to 2.56 s within 10 to 15 minutes of oxytocin application. This synchronisation was a likely cause underlying oscillations in isometric force observed in the organ bath experiments. Addition of the gap junction inhibitor carbenoxolone (200 μM) prevented synchronisation of Ca oscillations indicating that gap junctions are involved in this process.