Methods for detecting target nucleic acid molecules in a sample are provided. The methods involve hybridizing the nucleic acids or nucleic acids which represent complementary or homologous sequences of the target to an array of nucleic acid probes. These probes include a double-stranded portion, a single-stranded portion and a variable sequence within the single-stranded portion, where the single-stranded region of the probes includes a sequence complementary or homologous to a sequence of the target nucleic acid to be detected. The molecular weights of the hybridized nucleic acids of the set are determined by mass spectroscopy, and from the molecular weights of the hybridized probes, the presence of the target nucleic acid is detected by the presence of its sequence in the sample.