Introduction. Use of cocaine base paste (CBP) has had public concern in Chile, though little or no information about its clinical features is available. An exploratory-descriptive study is designed for gathering clinical data. Material and methods. Clinical features of 61 low income users randomly selected in a drug users therapeutic center are registered. Results. Averaging two months of regular use CBP provokes compulsive behaviors of searching and using the substance. It is a conditioned addiction since compulsive behavior only arouses as an external (mainly possession of money) or internal (mood changes and phantasy of smoking CBP) stimulus elicited response. Very different patterns of substance use are present in the same individual along a brief lapse of time. Sensitization (motor hypertonia and stereotypes, paranoia and audithory, visual and kinestesic delusions, all transitory symptoms linked to the acute intoxication state) and tolerance (decrease and disappearance of the euphorizing effect) quickly develop. Sensitization and tolerance appear simultaneously and with compulsive behavior altogether. Each single episode of use ends usually with intense feelings of guilt, anxiety and suicidal ideation indeed. There is a frequent loss of social normatives establishing a psychopatic syndrome. Conclusions. CBP use is linked to changing patterns of behavior, conditioned to external or internal stimuli with little if any relation to euphoria, suggesting a phenomenal associated to the neurobiology of learning