In mammals with binocular vision, projections of retinal axons to primary retino-recipient nuclei establish a strict visuotopic and eye-segregated arrangement. Normal primate visual pathway organization is characterized by orderly hemiretina separation in which nasal-retinal axons cross at the optic chiasm and project to primary contralateral subcortical and cortical structures while temporal-retinal fibres project ipsilaterally to corresponding visual structures. We report here, in two unrelated children, an unusual visual pathway malformation in which nasal-retinal cortical projections, unable to decussate due to the inborn absence of an optic chiasm, erroneously route ipsilaterally to visual projection targets. We have termed this newly documented achiasmatic condition the non-decussating retinal-fugal fibre syndrome (Apkarian et al., Invest. Ophthalmol. Vis. Sci., 34, Suppl., 711, 1993).