Quantitation of DNA is an important step for many practices in molecular biology. The concentration of a nucleic acid is most commonly measured by UV absorbance at 260 nm (A260). Absorbance methods are limited in sensitivity due to the high level of background interference. Hoechst 33258 dye, a bisbenzimide DNA intercalator, provides a fluorometric alternative that is more sensitive than UV absorbance methods. Hoechst 33258 excites in the near UV (350 nm) and emits in the blue region (450 nm). Sensitivity of the Hoechst 33258 dye is better than 10 ng/mL when it is detected with the GloMax® 20/20 Instrument and the UV Fluorescent Module.