The article deals with the concept of internal dialogue and its understanding in a variety of psychological schools in Russian and foreign psychology. A concept of internal dialogue is introduced as well as its understanding by M.M. Bakhtin, L.S. Vygotsky, G.M. Kuczynski, H. Hermans. The Internal dialogical activity Scale (IDAS) by P. Oles is presented. Russian adaptation of IDAS included two sections with an interval of two weeks between them. 256 respondents participated in the first section, and 123 of them in the second. The general ID score was validated; however, instead of replication of the original 7-factor structure, we revealed a more justified, reliable and valid 3-factor one (internal dialogue, internal world, internal conflict). Construct validity is underpinned by high correlations of IDAS factors with other measures of reflexive processes and aspects of self-attitude. Unlike the differential reflectivity test by D.A. Leontiev and E.N. Osin, IDAS seems to represent mostly the negative pole of self-reflection; this conclusion is based on the analysis of IDAS connections with other personality variables. Russian adaptation of IDAS can be used for research purposes and for practical work.