TiO2 fibers were formed by thermal treatment of layered H2Ti4O9 (hydrous titanium dioxide) and KHTi4O9 synthesized by ion-exchange reactions, The calcination of the former at 900 degrees and 1050 degreesC for 3 h yielded TiO2 fibers with anatase and rutile phases, whose length and diameter were 15-20 and 2-5 mum and 10-15 and 3-5 mum, respectively. The thermal treatment of the latter at temperatures of 250 degrees to 500 degreesC yielded pure K2Ti8O17, which tended to decompose to K2Ti6O13 and TiO2 at temperatures > 600 degreesC. At 1050 degreesC, K2TI6O13 phase was formed with rutile TiO2 fibers, whose length and diameter were 10-20 and 1-3 mum, respectively.