The article considers the typical mistakes made by investigators in applying the preventive measure in the form of a written pledge not to leave the place and proper conduct, such as insufficient motivation for the necessity of its choosing, unreasonable refusals to let the person leave the territory for the short period of time. Particular attention is paid to the need to obtain the consent of the suspect himself, accused of applying this preventive measure. The issues of interrelation between the applied preventive measure and the nature of the testimony given by the accused, the suspect, were touched upon. The author, with reference to foreign experience, suggests ways to improve the institution of a written pledge in Russian criminal process.