The goal of this work was to understand the key factors determining the DNA compacting capacity of single-chained cationic surfactants. Fluorescence, zeta potential, circular dichroism, gel electrophoresis and AFM measurements were carried out in order to study the condensation of the nucleic acid resulting from the formation of the surfactant-DNA complexes. The apparent equilibrium binding constant of the surfactants to the nucleic acid, K-app, estimated from the experimental results obtained in the ethidium bromide competitive binding experiments, can be considered directly related to the ability of a given surfactant as a DNA compacting agent. The plot of In(K-app) vs. In(cmc), cmc being the critical micelle concentration, for all the bromide and chloride surfactants studied, was found to be a reasonably good linear correlation. This result shows that hydrophobic interactions mainly control the surfactant DNA compaction efficiency. (C) 2018 Elsevier Inc. All rights reserved.