The study considers the topic of linguistic register by examining how schoolchildren, adolescents, and adults vary the texts that they construct across the dimensions of modality (spoken/written discourse) and genre (narrative/expository discourse). Although register variation is presumably universal, it is realized in language-specific ways, and so this analysis focuses on Israeli Hebrew, a language that evolved under peculiar socio-historical circumstances. An original procedure for characterizing register — as low, neutral, or high — was applied to four text types produced by the same speaker-writers. It was found that across all age groups, “neutral” items constituted the bulk of the material, and that the lexicon accounted for some 80% of variation. Developmentally, it was found that acquisition of fully flexible register variation continues beyond adolescence. Finally, it was observed that text types range on a cline from everyday colloquial usage in oral narratives to more formal, high-level language in written expository essays. These results are discussed in light of their implications for the nature of register variation, later language development, and the sociolinguistics of contemporary Hebrew.