After a brief introduction to the subject and the hypotheses put forward by the author, the paper looks into the source language (SL) text parameters relevant to its comprehension. Under this heading, the author names the unidirectionality of the SL text delivery and the multidirectionality of the comprehension process and some methods of measuring the ease/difficulty of the SL text. The next main item is the simultaneous interpreter’s processing capacity. Under this heading, the author discusses the feeling of familiarity and the familiarity coefficient. Finally, she formulates some conclusions.