The protein CEP290 has recently emerged as a major player in the biology of the cilium and as a causative protein in a number of human syndromic diseases, most of which are associated with the devastating blinding disease Leber congenital amaurosis. (Coppieters et al., Hum Mutat 31, 2010, 1097-1108) CEP290 is known to be an important component of the primary cilium, localizing to the Y-links of the ciliary transition zone and having a role in the regulation of transport in and out of the ciliary compartment (Craige et al., J Cell Biol 190, 2010, 927-940). While many mutations in CEP290 have been identified in human patients, how these mutations result in the spectrum of human disease attributed to the protein remain unknown. As we begin to learn more about the normal role of CEP290, it is likely that we will begin to shed light on how these mutations result in the various CEP290 disease phenotypes. Here we discuss many of these diverse aspects of CEP290 biology and pathology in an attempt to link what we know about the molecular mechanisms of CEP290 function with what we know about CEP290-associated disease.