FIELD DETENTION IS DEFINED AS A LEGITIMATE INVESTIGATORY TOOL: (1) WHEN THE POLICE ARE AS YET UNCERTAIN WHETHER ANY CRIME HAS OCCURRED; (2) AT THE SCENE OF A KNOWN OFFENSE WHEN QUESTIONING SUSPECTS AND OTHERS WHO MIGHT HAVE INFORMATION ABOUT THE CRIME; (3) TO IDENTIFY PERSONS FOR WHOM A WARRANT OR PROBABLE CAUSE FOR ARREST ALREADY EXISTS. AN EXPLANATION OF THE CONTROVERSY SURROUNDING THE PRACTICE OF FIELD DETENTION FOCUSES ON THE ISSUE OF PROBABLE CAUSE AND THE RIGHTS OF CITIZENS UNDER THE FOURTH AMENDMENT. THE NEED FOR DETENTION IS BASED ON PREVENTING LOSS OF LEADS, DESTRUCTION OF EVIDENCE, DISAPPEARANCE OF SUSPECTS OR WITNESSES, AND THE STIGMA OF FORMALLY ARRESTING AN INNOCENT PERSON. THE DEVELOPMENT OF CASE LAW CONCERNING THE DISTINCTION BETWEEN ARREST AND DETENTION IS TRACED FROM EARLY ENGLISH LAW THROUGH FEDERAL AND STATE DECISIONAL LAW. THE STATUTORY FORMULATIONS WHICH HAVE SET THE PRECEDENCE FOR DEALING WITH STOP AND SEARCH AND THE RIGHTS OF CITIZENS ARE ANALYZED, INCLUDING THE UNIFORM ARREST ACT OF 1941, THE NEW YORK STOP AND FRISK LAW OF 1964, AND THE AMERICAN LAW INSTITUTE'S MODEL OF PRE-ARRAIGNMENT PROCEDURE. THE QUESTION OF THE USE OF ROADBLOCKS (REGULATORY, INVESTIGATORY AND LIMITED) IS RELATED TO THE PROBLEMS OF STOP AND SEARCH. A LEGISLATIVE SOLUTION IS PROPOSED WHICH DEALS WITH THE ISSUES OF DETENTION OF SUSPICIOUS PERSONS, ROADBLOCKS, FRISK FOR DANGEROUS WEAPONS, THE WARNING OF RIGHTS, ARREST WITHOUT A WARRANT, REMAND FOR FUTHER SCREENING, THE DETENTION OF WITNESSES, AND THE RECOVERY OF CIVIL DAMAGES. AN EXPLANATION OF THE TERRY V. OHIO DECISION WHICH DEALS WITH A SUPREME COURT DECISION ON STREET ENCOUNTERS IS OFFERED IN AN EPILOGUE. FOOTNOTES AND REFERENCES BY CHAPTER ARE INCLUDED.