This thesis brings together two different lines of research, the nature of passive voice, the nature of readability. Commonly, languages have a range of tools for detransitivisation, topicalisation, and impersonalisation, of which passivisation is one (Givón, 1981). Passives have important roles in our language, and prescribing against their use lacks a full understanding of these roles. Much of the concern around passives from writers, editors, and teachers is no more than folklore that has not clearly analysed various writing and reading problems. Many awkward sentences are not awkward because they use passives but because they are wordy, clumsy, or pretentious. Most criticisms have little basis in linguistic theory, and rarely is there more than passing mention of the important role that passives play in communication. Some uses of passives are inappropriate, being vague, ambiguous, or even deceitful. These inappropriate uses of passive voice give the construction a bad name. They have become ammunition for prescriptive grammarians to fire at all uses of passives, often with weak analysis and minimal reference to linguistic theory. ‘Avoid passives’ has become a mantra. I tentatively suggest that there is unlikely to be a cost to processing passives. Given the speed at which the brain processes clauses, any differences in readability (if they exist) must be miniscule. Consequently, I suggest that any differences are unimportant relative to the benefits that appropriately used passives bring to readability. Furthermore, appropriately used passives may actually improve readability, especially when there is greater interest in the passive subject than the active subject, and when the passive serves to connect clauses or sentences.