A rapid and sensitive method for the detection of DNA in CsCl gradients is described, which is based on the complex formation between DNA and the intercalating dye ethidium bromide after fractionation of density gradients. Since no dye need be used in the original sample/CsCl mixture disadvantages such as dialysis, shaking with n-butanol, and/or running through a Dowex column can be avoided. Due to its sensitivity for nucleic acids (0.022 μg for DNA and 0.10 μg for RNA) this technique is most useful for small amounts of DNA, which are difficult to detect with a normal recording system or if no recording system is available at all.