This study investigated the orthographic and phonological contribution of visually masked primes to reading aloud in Dutch. Although there is a relatively clear mapping between the spelling and sound of words in Dutch, words starting with the letter c are ambiguous as to whether they begin with the phoneme /s/ (e.g., citroen, "lemon") or with the phoneme /k/ (e.g., complot, "conspiracy"). Therefore, using words of this type, one can tease apart the contributions of orthographic and phonological activation in reading aloud. Dutch participants read aloud bisyllabic c-initial target words, which were preceded by visually masked, bisyllabic prime words that either shared the initial phoneme with the target (phonologically related) or the first grapheme (orthographically related) or both (phonologically and orthographically related). Unrelated primes did not share the first segment with the target. Response latencies in the phonologically related conditions were shorter than those in the unrelated condition. However, primes that were orthographically related did not speed up responses. One may conclude that the nature of the onset effect in reading aloud is phonological and not orthographic.