Possible structural aspects are discussed that justify the different resistance to reduction of 2,3,5-triphenyl-2H-tetrazolium chloride (TTC) both chemically (by reaction with ascorbic acid (ASC)) and electrochemically, in the presence of different polyelectrolytes Such as poly(sodium 4-styi-enesulfonate) (PSS), poly(sodium 4-styrenesulfonate-co-sodium maleate) at two different comonomer compositions (P(SS1-co-MA(1)) and P(SS3-co-MA(1))), and poly(sodium acrylate-co-sodium maleate) (P(AA1-co-MA(1))). Different dissociation constants are found for the complexes between TTC and the different polyelectrolytes by diafiltration (DIF). Related to this, spectroscopical differences are also found by H-1 NMR and UV-vis spectroscopies. Dynamic light scattering (DLS) showed a higher tendency to undergo intermolecular aggregation for P(SS1-co-MA(1)) in the presence of TTC, a result that could be related with a higher tendency for TTC to form hydrophobic ion pairs as a consequence of single stacking with the benzene sulfonate groups (BS) of this polyelectrolyte. On the other hand. the lower tendency for PSS to undergo intermolecular aggregation could be attributable to a higher probability to form more hydrophilic adducts by means of double stacking with TTC.