Thripidae, one of the largest families of Thysanoptera, is widely distributed throughout the world. To explore the phylogenetic relationships and current classification of Thripidae, a cladistic analysis is presented based on 117 morphological characters scored from 114 species representing 94 genera. This analysis was used to reconstruct the ancestral feeding habits of Thripidae, with the result that leaf-feeding is recognised as ancestral within this family, and flower-feeding derived. Thripidae is recovered as a monophyletic group, but the three subfamilies Dendrothripinae, Sericothripinae and Panchaetothripinae are all recovered as nested within the fourth and major subfamily Thripinae. Sericothripinae is related to the Scirtothrips genus-group in Thripinae, but a close relationship to Echinothrips is not supported. Intergeneric relationships within Dendrothripinae are relatively well resolved. Three tribes in Panchaetothripinae are not monophyletic but Tryphactothripini genera form a clade with Panchaetothrips. Subfamily Thripinae is paraphyletic, but includes several monophyletic genus-groups (Rhamphothrips genus-group, Trichromothrips genus-group, Thrips genus-group, Frankliniella genus-group, Chirothrips genus-group). Relationships within the Thrips genus-group are poorly resolved, presumably due to a high degree of homoplasy. Five genera (Amomothrips, Moundinothrips, Smilothrips, Ctenothrips and Sciothrips) are placed into the Taeniothrips genus-group, and three genera (Salpingothrips, Tusothrips and Chaetanaphothrips) are proposed as the Chaetanaphothrips genus-group. The previously accepted Anaphothrips genus-group and Mycterothrips genus-group are not recovered, presumably because the supporting characters are merely superficial resemblance with no phylogenetic significance. This work resolves the systematic relationships among most thripid genera, as well as providing a morphological background for the evolution of Thripidae.