Data from a network of electric field mills at the NASA Kennedy Space Center have been computer analyzed to determine the parameters of a charge model that describes the locations and magnitudes of the net changes in the cloud charge distribution that are caused by cloud-to-ground lightning. The results are limited to relatively large events that can be described by a point-charge model, i.e., discharges that produced field changes of at least 1 kV m-1 at three or more sites and that have enough spatial symmetry to fit the model. The focus of effort has been to determine how the altitudes and magnitudes of different but comparable events vary from flash to flash, throughout the evolution of a storm, and from storm to storm. Tee results for seven small to medium thunderstorms in 1976, 1977, and 1978 indicate that the X, Y locations tend to cluster in cells with an overall dimension of 5 km or less and that the altitudes are surprisingly constant from flash to flash and throughout the day. Different storm days produced mean altitudes that range from 6.9 km (-14 ¿C) to 8.8 km (-26¿C), and the standard deviations are usually less than 20% of the mean. The average values of the charges that are deposited on different days range from 11 ¿C to 44 ¿C, and the standard deviations are typically 50% of the mean. The charges in two small storms exhibited 5-min running means that increased by 80% or more and peaked as the lightning rate was decreasing. Errors in the charge parameters that might be caused by a nonspherical charge geometry fitting the point-charge model were simulated by assuming that the lightning deposited a flat and horizontal disc of charge at various locations over the network. For disc radii of 5 km or less than standard deviation of the X-Y position error at different disc locations was less than 2 km. The errors in the disc charge values and altitudes at different locations had standard deviations that were less than 20% and 10% of the means, respectively; but there was a systematic increase in the charge and a lowering of the height when the disc moved off the network.