The investigative process that Department of Justice (DOJ) attorneys must follow in antitrust matters and their sources of information are described. Knowing the probable sources of a complaint is helpful in devising an initial defense strategy, particularly if information has come from a disaffected employee or conspirator. Potential conflicts between an employee and a corporation are addressed, beginning with an individual's fifth amendment rights against self - incrimination. Considerations in dealing with the subpoena duces tecum served to a corporation are examined, including negotiation with the Government, procedures to prevent destruction of relevant documents, and employees' personal files. The discussion of the subpoena ad testificandum delivered to an individual client emphasizes that intentions to seek immunity should be communicated to the DOJ as early as possible and that the attorney should meet with DOJ staff to advise them about the type of information the client has before the client makes any statement. Procedures governing immunity orders are outlined. A review of grand jury procedures which the witness should know covers the sequence of questioning, the right to consult with counsel and view documents, and ramifications of the immunity order. The client should be debriefed immediately after testifying, and this exchange is protected by the attorney client privilege unless either party reveals its contents to others. Tactics are also suggested for handling problems with prosecutors and the indictment. Approximately 30 footnotes are provided.