Effects of morphologically related primes were examined in two masked prime experiments. Responses to both free root and derived suffixed word targets were facilitated when primes were derived suffixed words containing the target's root, and this facilitation effect showed a time course similar to that for the facilitation effect of repetition primes (though systematically smaller in magnitude). In a control experiment only the longest prime duration of Experiment 1 was used; responses to derived suffixed word targets were facilitated by both free root primes and derived suffixed word primes sharing the target's root (relative to unrelated and form-related control primes). The free root and derived suffixed word prime conditions did not differ significantly. in Experiment 2, only true derived word primes produced facilitation whereas morphologically simple primes containing a pseudoroot did not influence performance relative to the unrelated prime condition. We argue that this supports a supralexical account of morphological representation.