Virtually all documents, computer data, and conversations have potential as an espionage target. Competitive industrial intelligence may be domestic as well as foreign-directed. Computerized data storage is particularly vulnerable. Although espionage in the United States is illegal, consistent enforcement is lacking. Each company should conduct a formal survey to assess the needs for asset protection. Security should note the seven categories of investigation: communications, undercover assignments, double agents, escape routes, reconnaissance, surveillance, and background investigation. Categories of scientific and technical aids to investigation include aids for data collection, aids for research, aids for identification, and aids for surveillance. Research and analysis are critical elements of each investigation, and intelligence is the product of analysis. Four common errors in analysis are overlooked threats, mistaken suspects, generalized conclusions, and erroneous conclusions. Private owners, in particular, should seek competent security directors and provide adequate resources for their security departments. Security directors should use countermeasures before industrial espionage occurs. An electronic surveillance glossary, about 85 references, and an index are included.