Some research suggests that semantic diversity (SemD), a measure of the variability of contexts in which a word appears, plays an important role in language processing, determining the availability of word representations (e.g., Adelman et al., 2006) and causing task-specific benefits or detriments to performance (e.g., Hoffman & Woollams, 2015). Some researchers have claimed that word frequency has no effect once such diversity measures are taken into account (Adelman et al., 2006). Taking advantage of the power of five large-scale databases, we investigated the effects of SemD, word frequency, and their interaction in five tasks, including word reading, lexical and concreteness decision, object picture naming, and word repetition. We found: (a) word frequency and SemD effects were consistently distinct; (b) effects of SemD were facilitatory in nearly all tasks, but inhibitory effects were also found; contrary to existing claims, we conclude that inhibitory SemD effects do not necessarily imply semantic selection requirements; (c) the presence of SemD effects minimally influenced the size of frequency effects when SemD was left uncontrolled, suggesting that SemD does not explain absent frequency effects in the patient literature; and (d) word frequency and SemD only interact in the largest data sets. Results are discussed in the context of rational models of memory (Anderson & Milson, 1989; Anderson & Schooler, 1991) and the Controlled Semantic Cognition framework (Lambon Ralph et al., 2017).