Positive ion electrospray ionization mass spectra have been obtained of deoxyribonucleic acids (DNA) and ribonucleic acids (RNA), including transfer RNAs (77-mer, ∼ 25 kDa). For several different solution conditions, the charge state distributions of DNA and RNA molecules were determined. It is postulated that the production of the multiply charged positive ions results from gas phase dissociation of complexes between nitrogen-containing bases and oligonucleotides.