The morphology of condensates formed between plasmid DNA and a PEG-poly(amidoamine) triblock copolymer were investigated using TEM and AFM in aqueous conditions. Both techniques revealed the presence of ring and extended linear structures; however, a greater proportion gf linear structures was obtained with the PEG copolymer than was seen with the poly(amidoamine) homopolymer, indicating that the PEG was interfering with condensation. Differences in the ring diameters between the PEG copolymer and the homopolymer were more marked with TEM than AFM, suggesting that compact toroidal structures are largely due to constriction on dehydration and that this is prevented from occurring in the presence of PEG. AFM revealed an increase in condensate size with increasing polymer/DNA ratio, which can be attributed to the association of more polymer with the complex. With TEM, the proportion of linear structures increased with increasing polymer/DNA ratio, whereas it remained relatively constant for AFM, across all ratios. It is suggested that an increased amount of PEG associated with the complexes promotes disruption of the ring structure upon dehydration. This supports the hypothesis that rings are formed via the bending of linear structures, with an equilibrium existing between the two, that is altered in favor of the linear structure by PEG.