"Galaxy conformity" is the observed effect whereby the star-formation state of galaxies (i.e. whether it is actively forming stars, or passive) is correlated from galaxy to galaxy on some spatial length scale. We first clarify the meaning and significance of conformity before examining the evidence for conformity on different scales. Galaxy conformity within large haloes is well established and is surprisingly strong. Although still poorly understood, it gives important clues to the physical quenching of star-formation in both central and satellite galaxies. Galaxy conformity on much larger scales is more controversial. We re-examine the evidence that has been presented for conformity on scales up to several Mpc, and show that this does not support the idea of physical effects operating on scales well beyond those of individual haloes.