Objective: The Diagnostic and statistical manual of mental disorders, third edition (DSM-III), published by the American Psychiatric Association (APA) in 1980, included the first official definitions by the APA of tobacco dependence and tobacco withdrawal. Tobacco industry efforts to influence the DSM-III were investigated. Method: Searches of previously secret tobacco industry documents, primarily the University of California San Francisco Legacy Tobacco Documents Library and British American Tobacco collections. Additional information was collected through discussions with editors of DSM-III, and library and general internet searches. Results: The tobacco companies regarded the inclusion of tobacco dependence as a diagnosis in DSM-III as an adverse event. It worked to influence the content of the DSM-III and its impact following publication. These efforts included public statements and private lobbying of DSM-III editors and high ranking APA officers by prominent US psychiatrists with undisclosed ties to the tobacco industry. Following publication of DSM-III, tobacco companies contracted with two US professors of psychiatry to organise a conference and publish a monograph detailing controversies surrounding DSM-III. Conclusions: The tobacco industry and its allies lobbied to narrow the definition of tobacco dependence in serial revisions of DSM-III. Following publication of DSM-III, the industry took steps to try to mitigate its impact. These actions mirror industry tactics to influence medical research and policy in various contexts worldwide. Such tactics slow the spread of a professional and public understanding of smoking and health that otherwise would reduce smoking, smoking induced disease, and tobacco company profits.