Interactions between fair-weather cumulus clouds and mixed-layer thermals were the focus of a one-month field experiment in Oklahoma. This experiment, called Boundary Layer Experiment—1983 (BLX83), combined remote sensors, surface observations, balloon platforms, and aircraft measurements to study the kinematics at the top of the daytime convective boundary layer. Emphasis was placed on the study of the entrainment zone, and on the relationship between individual therma1s as identified by lidar and turbulent motions and fluxes as measured by aircraft and sodar.