Utterance planning is the part of language production that converts an idea into an ordered sequence for articulation. I’ll argue that this process has certain properties that create systematic biases in speakers’ unconscious choices of sentence structures. For example, utterance planning has inherent memory demands, and the representation of the intended sentence can degrade in memory when similar parts of the utterance plan interfere with each other. This memory interference increases production difficulty, and speakers reduce interference by adopting sentence structures that let them omit or delay interfering elements. I’ll present data from corpora and production experiments linking memory interference to two omission phenomena, rates of null subjects in Mandarin and use of bare passives (omitting the agent) in six languages. These and other results suggest that the nature of utterance planning has an explanatory role in accounting for the distribution of syntactic structures in a language. I’ll point to potential consequences for language comprehension, acquisition, and typology.