The solubility, sedimentation, circular dichroism (CD) and absorption spectral characteristics of calf thymus DNA were examined in concentrated solutions of LiCl (6-13 M) at 25-27.degree. C. At all concentrations of LiCl, the DNA is base stacked and exhibits normal hypochromicity. At the upper end of this range of LiCl concentrations, DNA aggregates and ultimately precipitates completely from solution between 13-14 M LiCl. This aggregation process is dependent on concentration, base composition and MW of DNA. The sedimentation velocity data taken together with the absorbance spectral data suggest that the aggregation process leading to the formation of large structures begins at .apprx. 9 M. Prior to the onset of aggregation, the CD spectra can be adequately fitted by a linear combination of contributions of the B, C and A forms of DNA. Above 9 M LiCl, both factor analysis and a primitive version of matrix rank order analysis indicate that at least 1 additional spectral component is required to account for the observed CD spectra above 260 nm. The general shape of this additional component or distortion resembles the .psi. form of DNA.