This paper studies various types of inaccuracies in the existing descriptions of the Russian grammar. These inaccuracies derive from different sources. In some cases, we deal with an oversight in the description, and a correction of the inaccuracy does not generate new linguistic knowledge. Such inaccuracies are of little interest. We deal with the contrary situation if the inaccuracy in the grammatical description stems from the fact that some phenomena have not come into the view of the grammarian. Here, one can correct the inaccuracy only if the linguist uncovers the phenomenon that other grammarians have overlooked. In other cases, we come up against the inconsistency between different parts of the description. Here, there may be various ways to make the description consistent, but in any case, we must abandon some of the contradictory statements. One should distinguish such cases from the cases when the description is not explicit enough, and one might make it technically correct (perhaps not the best one though) by means of special clarifications. It is important to keep in mind the consequences of such clarifica- tions: every so often they result in an increasingly large and overly complex grammatical description (or some of its parts). Moreover, in some cases, an attempt to save the existing description by means of clarification causes the grammatical rules to be unnatural.