The vertebrate body plan features a left-right (LR) asymmetry, but how the LR axis is orientated correctly with respect to the anteroposterior (AP) and dorsoventral (DV) axes is not known. Here, Jeffrey Amack and co-workers (p. 45) report that the Rho kinase Rock2b links AP patterning to LR patterning in zebrafish embryos. During development, Kupffer's vesicle (KV) generates a cilia-driven leftward fluid flow that directs LR patterning. The authors demonstrate that depletion of rock2b in whole embryos or in the KV cell lineage alone disrupts asymmetric gene expression during development and perturbs organ asymmetries. They show that, in control embryos, ciliated cells are distributed asymmetrically along the AP axis of the KV and generate asymmetric fluid flow. By contrast, rock2b knockdown embryos show defective KV patterning and cell morphology, and a loss of directional flow. Based on their studies, the authors propose that Rock2b is required for the AP positioning of ciliated cells within the KV and for subsequent LR patterning in zebrafish embryos.