Small holes in membranes or nanocapillaries can be employed to detect single molecules in solution. In fact, the resistive-pulse technique based on nanopores allows for determination of length, charge, and folding state of deoxyribonucleic acid (DNA). Here, we describe the experimental procedures necessary for measuring single DNA molecules in nanocapillaries. We also discuss the measures for data analysis and how to determine that only single molecule events are observed.