A numerical model of miniature endplate current (mepc) generation was fitted to the rising phase of individual mepcs recorded at the frog neuromuscular junction, and estimates of 6 transmission parameters were obtained. Model fitting was enabled by assuming literature values for geometric parameters and determining single channel current by noise analysis, the channel closing rate constant from the mepc decay, and acetylcholine hydrolysis parameters from mepcs recorded in esterase-blocked endplates. Under control conditions, mean estimates were: number of molecules in a quantum = 29,000, diffusion coefficient = 2.8 × 10 −6cm 2s −1, endplate receptor density = 8500 μm −2, forward binding rate constant = 7.6 × 10 8 M −1s −1, equilibrium dissociation constant = 58 μM and channel opening rate constant = 8100 s −1.