This paper applies semantic and syntactic analytical devices and relies on the concept of metaphor of cognitive linguistics to find out under what circumstances derivatives of verbs with the verbal particle 'bele' (into) and those with 'be' (in) can be mutually substituted for one another, as well as what occurrences can be typically restricted to one or the other particle. Three typical cases of the use of those two particles can be differentiated. 1. Their functions are strictly disjoint. The main factors that may frustrate their interchangeability are as follows: the grammaticalization of 'be', the evacuation of its directional meaning (its becoming a marker of perfectivity); semantic properties of the arguments (e.g., only derivatives involving 'be' occur with arguments meaning any kind of 'room', whereas certain 'container' metaphors attract forms involving 'bele'). - 2. The functions of the two particles largely overlap, with just a few exceptions. In such cases, no syntactic consequence can be observed in the phrases involving the verbs (a 'null morpheme' marking), a crucial but not indispensable requirement of interchangeability. - 3. In the most problematic groups of cases, to various extents, the occurrence of one of the two particles can be said to be more appropriate. 'Bele' can take over the role of 'be' mainly where the semantic character of 'material' or 'container' of the illative argument is foregrounded.