Polyacrylonitrile (PAN) hollow fibers were pretreated with five different compounds containing phosphorus, including ammonium dibasic phosphate, ammonium dihydrogen phosphate, triammonium phosphate, phosphoric acid, and metaphosphoric acid, and then further oxidized in air, carbonized in nitrogen, and activated with carbon dioxide. The effects of different compounds containing phosphorus as pretreating agents on the properties and structure of the resultant oxidized hollow fibers, carbon hollow fibers, and activated carbon hollow fibers are discussed. Comparing the Brunaner-Emmett-Teller (BET) surface area of PAN-activated carbon hollow fibers (ACHF) pretreated with five different compounds, ammonium dibasic phosphate > triammonium phosphate > ammonium dihydrogen phosphate > phosphoric acid > metaphosphoric acid, and the surface area of mesopores in PAN-ACHF pretreated with ammonium dibasic phosphate reaches maximum, 174 m(2) g(-2). The adsorption ratio to mesomolecule adsorbate, VB12 of PAN-ACHF pretreated with ammonium dibasic phosphate also reaches maximum, 97.7 wt %. Moreover, the dominant pore sizes of PAN-ACHF range from 2 to 5 nm in diameter. (C) 2005 Wiley Periodicals, Inc.