Thanks to all who shared their preferences on quantifying DNA. My original question was: Dear colleagues, Which kind of instrument do you prefer to use to quantify DNA for use in sequencing? I have used the NanoDrop from Thermo, but was wondering if anyone has something else that you use. The most popular answer was the Qubit from Invitrogen. It is a fluorescence-based instrument that uses solutions that you add to your sample and measure, either on a plate reader or on their small footprint fluorometer. "The fluorometer uses an intercalating dye to bind to the DNA and then fluoresces when excited. This means that unlike the spectro based machines, the reading reflects only the DNA present in the sample and is not influenced by non-DNA which can influence the reading of a spec-based machine. For accuracy, I think the fluorometer is hard to beat." Others said they run their samples on an agarose gel, and compare band intensity to a sample of "known" concentration. They needed to make sure they had a PCR product anyway, and with practice is an easy way to "quantify." I knew about the pitfalls of UV/Vis measurements, but when the NanoDrop came along, its ease of use outweighed the problems. Now it sounds like the Qubit kits have made fluorescent measurements easier, so it is certainly worth consideration. Thank you all for your help, Ann R. Harris email: annharris@ou.edu