Online searches of bibliographic databases have lately included researching database records containing nucleic and amino acid sequences. As database producers recognize the importance of genetic sequence information, the number of databanks that include molecular sequence data is increasing. The National Library of Medicine includes GenBank and other research database accession numbers in the accession number field of the MEDLINE database. Over 15,000 accession numbers are retrievable in MEDLINE records dating as far back as 1971. The Scientific and Technical Information Network includes over 140,000 protein sequences in its Registry database. GENESEQ from Derwent is a database containing nucleic acid, protein, and probe sequences taken from patent applications. Advice on using the GenBank On-line Service is provided.