We investigated the phylogeny of tintinnids (Ciliophora, Tintinnida) with 62 new SSU-rDNA sequencesfrom single cells of 32 marine and freshwater species in 20 genera, including the ?rst SSU-rDNAsequences for Amphorides, Climacocylis, Codonaria, Cyttarocylis, Parundella, Petalotricha, Undellaand Xystonella, and 23 ITS sequences of 17 species in 15 genera. SSU-rDNA phylogenies sug-gested a basal position for Eutintinnus, distant to other Tintinnidae. We propose Eutintinnidae fam.nov. for this divergent genus, keeping the family Tintinnidae for Amphorellopsis, Amphorides andSteenstrupiella. Tintinnopsis species branched in at least two separate groups and, unexpectedly,Climacocylis branched among Tintinnopsis sensu stricto species. Tintinnopsis does not belong tothe family Codonellidae, which is restricted to Codonella, Codonaria, and also Dictyocysta (formerlyin the family Dictyocystidae). The oceanic genus Undella branched close to an undescribed fresh-water species. Metacylis, Rhabdonella and Cyttarocylis formed a well supported clade with severalTintinnopsis species at a basal position. Petalotricha ampulla and Cyttarocylis cassis SSU-rDNA andITS sequences were identical or almost identical. Therefore, we propose Cyttarocylis ampulla comb.nov. for them. Intensive use of single-cell isolation and sequencing revealed unexpected complexityin the evolutionary history of these relatively well-studied ciliates. Notably, the diversity of freshwaterforms suggests multiple marine-freshwater invasions.