We correlated cloudtop temperatures obtained from GOES-8 infrared images, lightning data from the National Lightning Detection Network, and triangulated nadir positions of sprites from a 22 July 1996 Mesoscale Convective System (MCS) over Kansas. The maximum sprite production of the MCS occurred during the transition between growth and decay phases of the system, and when the occurrence rate of negative cloud-to-ground (-CG) flash activity maximized. The -CG flash rate was maximum when the overlying cloudtop temperatures Tc were minimum, -69¿ to -72¿C. During the MCS growth phase, the -CG occurrence rate increased smoothly with decreasing Tc, and declined with increasing Tc during the decay phase. By way of contrast, the +CG rate remained associated with approximately constant Tc (-69¿ and -72¿C) during the growth phase, and then also declined with increasing Tc during the decay phase. The sprite-generating +CGs occurred in regions with cloudtop temperatures 2--3¿C warmer than the rest of the +CG population.