The authors review the evidence that repetitive administration of central nervous system stimulants and other compounds may be associated with progressively increasing effects on pathological behavior and seizures rather than tolerance. They suggest that the progressive effects of these compounds may be related to electrical kindling, a phenomenon in which repetitive subthreshold stimulation of the limbic system is eventually associated with major motor seizures. They review the studies supporting a pharmacological kindling mechansim and suggest a kindling model for psychological stimuli that combines neurophysiological, biochemical, and psychological perspectives.