Some heredomacular diseases share ophthalmoscopic and morphologic similarities despite being nosologically distinct. In part, this may arise from pathologic reaction patterns such as lipopigment accumulation and drusen deposition which are common to a variety of disorders of the photoreceptor--retinal pigment epithelium--Bruch's membrane complex. Two of these disorders, Stargardt's flavimaculatus and the pattern dystrophies of the retinal pigment epithelium may be especially difficult to differentiate clinically since they are characterised by both a similar ophthalmoscopic appearance and considerable inter and intrafamilial variation in their expression. Stargardt's flavimaculatus may, however, be distinguished from the retinal pigment epithelial pattern dystrophies by certain clinical and morphological features that are outlined below.