There is a commonly held view that structural change accompanying an electron-transfer reaction leads to the observation of sub-Nernstian behavior. This may be reasonable if the straightforward mechanism ne + O1 ⇄ R2 is operative. However, if part of the "square" scheme (Chemical Equation Presented) applies, this conclusion is shown not to be generally valid. The converse thesis that Nernstian behavior implies structural integrity is also not generally correct. Reactions that are part of the square mechanism may cause a reversible electron transfer to appear irreversible by decreasing the slope of the reduction wave. But our treatment shows that they may equally well increase the slope or leave it unchanged. Under other circumstances the reduction wave may split into two, or become preceded by a gratuitous peak. The present study convinces us that drawing mechanistic conclusions from voltammetric data alone is fraught with danger.