Evidence supports the proposition that the high affinity Ch uptake system associated with cholinergic nerve terminals can be the rate limiting step in the synthesis of the neurotransmitter, acetylcholine. The present experiment was designed to test the hypothesis that variations of the system would be reflected selectively in changes of conditioned avoidance behavior. HC-3, which primarily affects the high affinity component of Ch transport thus reducing endogenous levels of ACh and the synthetic capacity of cholinergic nerve terminals, was administered cerebroventricularly at 5 doses ranging from 0.0 (saline control) to 10.0 microgram. Whole brain ACh levels determined by GCMS analysis following microwave fixation ranged from 25.0 to 5.0 nmol/g-1. Trend analyses demonstrate a precise dose dependent relation between neurochemical and behavioral variables: median trials to condition increased as ACh level decreased. More detailed analyses of the results lead to the interpretation that suppression of high affinity Ch transport in brain is associated with deficiencies in the use of information and not with sensory input and storage nor with motor output.