The aim of this paper is to investigate mediopassive participle formation with respect to types of events. The basic insight is that telic verbs are related to m/p participles. A NP argument of a telic verb undergoes a definite change of state which is captured, in the grammatical level, by a form, i.e. the m/p participle, denoting a result state subsequent to the accomplishment of an event. Further questions such as thematic role structure come up in this connection. Thematic roles play an important part in classifying event types. They may be viewed, in this particular case, as a set of verbal entailments within a cluster-concept called “proto-patient”. Distinctions established with respect to thematic roles correspond to categorizations based on lexical aspect.