This paper provides taxonomic, distributional and ecological data for 59 species in 17 genera of Trechinae and Psydrinae from Tasmania, and describes 18 new species in six existing genera (Pterocyrtus, Tasmanorites, Sloanella, Trechistus, Goedetrechus, Tasmanotrechus) collected from caves, forest and montane habitats: Pterocyrtus grayi sp. nov., P. meridionalis sp. nov., Tasmanorites beatricis sp. nov., T. daccordii sp. nov., T. lynceorum sp. nov., T. microphthalmus sp. nov., Sloanella gordoni sp. nov., Trechistus gordoni sp. nov., Goedetrechus minutus sp. nov., G. rolani sp. nov., G. florentinus sp. nov., G. damperi sp. nov., Tasmanotrechus gordoni sp. nov., T. alticola sp. nov., T. montisfieldi sp. nov., T. osbornianus sp. nov., T. moorei sp. nov., T. rolani sp. nov. Forty-one (41) previously described species have been re-examined and illustrated with supplementary descriptions. New collection records combined with the published literature revealed 196 records of 83 species in 21 genera, collected from 41 localities (including 11 karst areas). Regional-scale survey coverage has been patchy and three biogeographic regions stand out as poorly surveyed: Flinders, South East, and Northern Midlands. Local-scale survey efforts have been intensive at just a few localities, the richest being 18 species recorded at Cradle Mountain. Seventeen (17) described species of Zolini and Trechini are troglobites with distribution ranges restricted to individual karst areas. Some karst areas and caves harbour multiple congeneric species which differ in their degree of troglomorphic specialization suggesting heterochronic colonisations, possibly linked to multiple Quaternary glacial / inter-glacial cycles. Palaeo-climatic and palaeo-vegetation evidence is examined to test the ‘Climatic Relict Hypothesis’ as a mechanism driving evolution of the subterranean fauna. It is proposed that present-day troglobitic Trechinae in Tasmania are derived from troglophilic progenitors that colonised subterranean habitats from adjacent forest ground litter habitats during Pleistocene inter-glacial periods, while retreat of forests during glacial periods isolated subterranean populations from surface populations facilitating troglogenesis. It is predicted that future collecting efforts will reveal many additional new subteranean species, including in non-karstic Shallow Subterranean Habitats (SSH).