The laws of many States permit such arrests, although the fourth amendment guarantees the right against unreasonable seizures. A custodial arrest is the paradigmatic seizure of the person and, therefore, falls within the scope of this amendment. A review of Supreme Court cases reveals that, rather than attempting to evaluate 'reasonableness' by ad hoc balancing of all the interests implicated in each individual case, the courts have been willing to formulate rules requiring varying degrees of particularized justification for varying degrees of intrusion upon individual fourth amendment interests. The results are sets of rules for different categories of situations in which significant variations exist in the level of government intrusivenes.. There is no reason why this approach should not be applied to the problem of custodial arrests. In order to give substantive content to reasonableness in such cases, a balancing of legitimate State interests against those individual interests which have been invaded in these arrests is required. Legitimate State interests include the need to ensure the appearance of the offender at trial, facilitation of investigation of the crime, incapacitation of the arrestee to protect the community, and the performance of welfare services. Individual interests include privacy, dignity, liberty, security, and freedom from arbitrary or discriminatory enforcement. These interests would best be balanced by a rule that fill custodial arrests for any minor offenses are unreasonable under the amendment unless the arresting officer can show probable or reasonable cause to believe that the arrestee will not appear for trial if summoned or will cause injury to himself or to others unless immediately taken into custody. The courts' application of this rule would full a serious gap in present fourth amendment doctrine and protect citizens. Related court cases are cited. Footnotes with references are included.