The "irreparable harm" standard is an old principle of equity designed to limit court use of injunctions to situations in which the absence of court intervention would produce irreparable injury to legally protected interests. This study describes and analyzes the courts' use of the irreparable harm standard in anti-strike injunction proceedings that involve teachers and school boards. The project includes analyses of previous litigation and legislation concerning the irreparable harm standard's use in teacher strikes. The major portion of the project involved gathering field data in settings where strikes and injunction proceedings occurred during 1978 and 1979. Field data are presented thematically rather than site-by-site. In addition, questionnaires were completed by 129 (82 percent) of the superintendents who experienced strikes during 1978-79. In the appendices are more detailed accounts of case law; data from a number of the field settings; a state-by-state inventory of pertinent statutory provisions; a comprehensive analysis of the treatment of the irreparable harm standard by the appellate courts; and the results of the questionnaire survey of superintendents who experienced strikes. (Author/MLF)