The goal of this paper is to clarify the categorial status of present participles. Present participles cross-linguistically exhibit properties of both verbs and adjectives. But can all present participles function in both ways? Based on numerous empirical tests, I will claim that while certain present participles are indeed ambiguous between a verbal and an adjectival reading, some of them are exclusively verbal. I will then suggest that the class of adjectival present participles can be defined aspectually: only participles of stative verbs can function as adjectives. An important consequence of the proposed analysis is that the prenominal position in English (and the post-nominal one in Hebrew) must be assumed not to be reserved for adjectives only, but to be able to host verbal elements as well.