The loss of hilar mossy cells (MC) is a common feature observed in the epileptic hippocampus, but despite a wealth of pathological data many physiological properties of MCs in the normal brain have still not been characterised. We have investigated if strong excitatory inputs from granule cells, intrinsic MC characteristics, either weak inhibition and/or integration favouring excitation can contribute to MC vulnerability. Rats (13-24 days old) were humanely killed by decapitation and the brain removed, and hippocampal acute slices or slice cultures were prepared. Using biocytin labelling, minimal stimulation and paired recordings, we have selectively activated individual excitatory and/or inhibitory inputs onto MCs and studied MC-evoked excitatory currents in dentate granule cells. Mossy cells were identified by the location of the soma, the presence of thorny excrescences on proximal dendrites and the pattern of axonal and dendritic arborisation, as visualised with light microscopy. MCs (n=15) displayed a characteristically large capacitance (215.40pF±15.83, mean±SEM), a sag in response to hyperpolarizing pulses (ratio=0.96±0.00), had a resting membrane potential of −62.71mV±2.03 and a membrane time constant of 49.67ms±2.65. Minimal stimulation within the granule cell layer (n=10) of acute slices evoked all-or-none unitary IPSCs in MCs, with amplitudes of 48.00pA±6.72, rise times of 0.60ms±0.05, decay profiles that were better fitted by a single exponential (τ=10.10ms±1.04). IPSCs were abolished by the GABA_A antagonist SR-95531 (1.2μM). Trains of stimuli, applied for 25ms at 40Hz, induced short-term depression of the IPSC (10th/1st IPSC=0.40±0.03). Conversely, minimal stimulation of granule cells evoked unitary EPSCs in MCs that facilitated when trains of 40Hz were applied and were inhibited by application of the group II metabotropic glutamate receptor (mGluRII) agonist, LY354740 (0.5μM). Paired recordings in slice cultures revealed that granule cells evoked large, monosynaptic EPSCs in MCs (173.88±82.97pA, n=5). These EPSCs displayed paired pulse facilitation in control conditions and were inhibited by application of LY354740 (0.5μM), whereupon an increase in failures was always observed. Furthermore, granule cell firing frequently entrained MCs. Paired recordings further demonstrated that MCs evoked much smaller (20.06±5.66pA, n=7) monosynaptic EPSCs in granule cells that tended to display paired-pulse depression. We conclude that hilar mossy cells receive strong and facilitating mossy fiber-mediated unitary EPSCs and short-term depressing unitary IPSCs.