The functions of Federal law enforcement are to inhibit and punish conduct that directly harms or threatens the Federal Government, its personnel, and property; to inhibit and punish antisocial conduct with which the States are unwilling or incompetent to deal; and to ensure compliance with Federal statutes and Federal regulatory processes. Much progress has been made in the effort to promote a climate of positive interchange between Federal police and non-Federal police such as information exchange, technical assistance, and multijurisdictional operational task forces. Incentives to communication, cooperation, coordination, and collaboration include the need to combat multijurisdictional criminals, the wish to share assets forfeited by drug offenders, the complexity of some crime, and the acquisition of additional and talented personnel. The tradition of self-governance, resource constraints and lingering skill and integrity deficits in some locales, information-processing constraints, and turf jealousies number among the disincentives to cooperation. An ongoing need for principles that help delineate the Federal police role is evident. 43 footnotes, 1 table, and 236 references