The self-assembling of DNA and cationic polymers are of interest for their biological applications. In this paper, the interaction of DNA with PAMAM was studied by agarose gel electrophoresis, size and zeta-potential measurements and circular dichroism (CD) spectroscopy. DNA was shown to form stable complexes with PAMAM by gel electrophoresis. The mean particle size of the complexes was in the range of 150-180 nm. The zeta-potential was positive and increased with an increase of N/P ratios. Compared to naked DNA, CD spectra of complexed DNA was changed and had a decreased intensity at 270nm. High salts and excessively low or high pH values could also result in decreased CD signals of PAMAM complexed DNA. These results provide some instructions for assembling of DNA as well as gene therapy applications.