OBJECTIVE: The authors' objective was to assess the frequency and nature of cocaine-induced paranoia. METHOD: They interviewed 50 cocaine- dependent men consecutively admitted to a 28-day rehabilitation program. RESULTS: Thirty-four (68%) of the 50 men reported highly distressing transient paranoid states in the context of cocaine use. The men who experienced paranoia did not differ from those who did not in age, race, or measures of cocaine use. The mean duration and amount of cocaine use before development of paranoia of the men who reported paranoia were not significantly different from the mean lifetime duration and amount of cocaine used by the men who did not report paranoia. Paranoia became more severe and developed more rapidly with continued cocaine use. CONCLUSIONS: The transient paranoid state appears to be a common feature of cocaine dependence and does not seem to be simply a result of exceeding a threshold of use. Rather, affected individuals might possess a predisposition to this drug-induced state. The fact that paranoia became more severe and developed more rapidly with continued drug use is consistent with a sensitization model of cocaine-induced paranoia. In vulnerable individuals, limbic sensitization may underlie its expression, but localization to a specific brain region is speculative. Quantity of use and route of administration do not appear directly to predispose to this phenomenon. Future investigations must be aimed at uncovering the markers and meaning of vulnerability to transient paranoia in heavy cocaine users.Abstract Teaser