The «Field» (trial by combat) is a procedural institution known to the sources of law of medieval Rus’ at least from the 13th century. For several centuries, the «field» was widely used as a means of proof, and was subject to detailed legal regulation as early as in the 15th century. A number of major regulatory legal acts regulated the conditions and procedure for the trial by combat, its legal consequences and the amount of «field duties». The possibility of participating in such a trial was also regulated by law in detail. The surviving materials of judicial practice make it possible to clarify this information and assert that the participants to the trial of combat could have been not only the plaintiff, defendant, witnesses and their «hires,» but also the judges who considered the case before the reporting procedure. In addition, slaves who represented their masters and were not considered «hiremen» could take part in a trial by combat. It should also be noted that, despite the negative attitude towards trials by combat on the part of the Russian Church, monks and clergy did not refuse to participate in the «field». At the same time, the legal papers show that they understood the bias of this means of proof and a gradual decrease in the number of fights, which became rare as early as in the 16th century, although the final disappearance of traces of this legal institution from legislation occurred only in the 17th century.