[Image:VirusBaltimoreClassification.svg|right|thumb|350px| The Baltimore Classification of viruses, created by the American biologist David Baltimore, is based on the method of viral mRNA synthesis]] The Baltimore classification, developed by David Baltimore, is a virus classification system that groups viruses into families, depending on their type of genome (DNA, RNA, single-stranded (ss), double-stranded (ds), etc.) and their method of replication.