We investigated the stability and developmental interplay of word reading and spelling in samples of Swedish (N = 191) and U.S. children (N = 489) followed across four time points: end of kindergarten, grades 1, 2, and 4. Cross-lagged path models revealed that reading and spelling showed moderate to strong autoregressive effects, with reading being more predictable over time than spelling. Regarding the developmental interplay, we found a bidirectional relationship between reading and spelling from kindergarten to Grade 1. However, starting in Grade 1, reading predicted subsequent spelling beyond the autoregressor but not the other way around. In all analyses, the findings were similar across the two orthographies. The theoretical and practical implications of these findings are discussed.