Electrodes bearing terminally attached PEG(600)-Fc and PEG(3400)-Fc chains exhibit remarkably similar time responses in cyclic voltammetry. Two asymmetrical NHS-PEG(600)-Fc and NHS-PEG(3400)-Fc poly(ethylene glycol) (PEG) chains of markedly different lengths were synthesized, and their activated N-hydroxysuccinimide ester (NHS) end was used for terminal attachment to the surface of a glassy carbon electrode. A similar surface coverage was obtained with both derivatives. At this coverage, the attached NHS-PEG(600)-Fc, which are relatively small, were not constrained to overlap whereas the attached NHS-PEG(3400)-Fc were necessarily stretched. The presence of the ferrocene (Fc) redox probe gave rise to signals in cyclic voltammetry which were analyzed quantitatively. At sufficiently high potential scan rate the peak currents reflect the flexibility of the terminally attached PEG chains. Both types of derivatized electrodes gave remarkably similar peak currents in cyclic voltammetry.