The effects of 9-amino-1,2,3,4-tetrahydroacridine (THA) and its fully aromatic analogue 9-aminoacridine (9-AA) on erythrocyte membrane morphology were investigated via scanning electron microscopy. The ghost population was categorized into four distinct classes and alterations in the relative amounts of these populations with drug addition were noted. The samples incubated in 9-AA had a significantly higher (p less than 0.001) flat, two-dimensional cell population. This shift in morphology may be attributable to the unwinding of spectrin and the subsequent collapse of the membrane.