This invention relates in general to a method for molecular fingerprinting. The method can be used for forensic identification (e.g. DNA fingerprinting, especially by VNTR), bacterial typing, and human/animal pathogen diagnosis. More particularly, molecules such as polynucleotides (e.g. DNA) can be assessed or sorted by size in a microfabricated device that analyzes the polynucleotides according to restriction fragment length polymorphism. In a microfabricated device according to the invention, DNA fragments or other molecules can be rapidly and accurately typed using relatively small samples, by measuring for example the signal of an optically-detectable (e.g., fluorescent) reporter associated with the polynucleotide fragments.