Traditional grammars regard simple intransitive verbs as a homogenous class. Generative Grammars contend the opposite, namely that they form a heterogeneous class as they manifest different semantic and syntactic properties. The purpose of the present study is to investigate these properties exhibited by simple intransitives contrastively via the generativist approach. According to the latter there are two types of one-argument verbs: unaccusatives and unergatives. The two subclasses are semantically and syntactically different. This distinction between the two subclasses is semantically predictable and syntactically encoded. We speak of semantic predictability since the two types have a different set of semantic properties which can often help to predict which of the two classes an intransitive verb belongs to. The most important semantic difference stems from the different thematic role which they assign to their argument. Thus, unaccusativity has been associated with non-agentivity, whereas unergativity has been associated with agentivity. We will try to see to what extent such semantic and syntactic properties of the two subclasses are checked equally in the two languages subject to investigation, namely English and Romanian.