Mediated priming (MP) presumably occurs via a mediating item (e.g., LION primes STRIPES via TIGER; Balota & Lorch, 1986). McKoon and Ratcliff 1988 argue that MP is caused by weak, but direct, prime-target relationships. Semantic relatedness and lexical co-occurrence underlie this effect. We replicate the MP effect (lexical decision and naming). Using the HAL memory model, we find that mediated to target semantic distances are greater than unrelated pairs, and find no relationship between strength of primig and lexical co-occurrence. McKoon and Ratcliff's claims find no support from these results. We conclude that MP occurs as a function of contexts shared (or mediated) by the mediating prime and the mediator itself.