The goal of the present study was to test theories about the extent to which individual differences in word reading align with those in spelling and the extent to which other cognitive and linguistic skills play different roles in word reading and spelling. Using data from 1,116 children ranging from 8 to 17 years, we modeled word reading and spelling as latent traits with two measures of each skill to reduce measurement error. The models also included five skills that have been theorized to relate differentially to reading and spelling: phonemic awareness, working memory, rapid automatized naming, arithmetic, and vocabulary. The latent-trait correlation for reading and spelling was very high, 0.96, although significantly less than perfect. Vocabulary correlated more strongly with reading (0.64) than spelling (0.56), but the correlations of the other skills with reading and spelling did not differ significantly. Breaking down the sample by age, we found a significantly higher latent-trait correlation between reading and spelling in the younger half (r = .98) than in the older half (r = 0.94). This difference may reflect the fact that the words on reading and spelling tests are more different from one another at older ages. Our results suggest that word reading and spelling are one and the same, almost, but that spoken vocabulary knowledge is more closely related to reading than to spelling.