Bismuth-based high Tc superconductors have been prepared as fibers by a technique of melt extraction. As-made, the fibers are amorphous with diameters ranging from 0.7 μm to 100 μm and lengths of up to 5 cm. The fibers were subsequently transformed into high Tc superconductors by heat treatment in air. Superconducting transitions at 105 K and 82 K were measured in annealed fibers of initial composition Bi1.8Pb0.2Sr2Ca3Cu4Ox by SQUID magnetometry. The volume fractions of superconducting phases were estimated to have lower bounds of 30% for 2212 and 5% for 2223. The crystallization process has been studied by differential scanning calorimetry, electron microscopy, and x-ray diffraction. Crystallization involves first the formation of the Bi-2201 phase and a bcc phase with lattice parameter a = 0.425 nm before finally significant fractions of both the Bi-2212 and Bi-2223 phases are formed.