Fibers spun from anisotropic solutions of a lyotropic rigid-rod polymer, poly(para-phenylene benzobisthiazole) [PBZT], were coagulated into homogeneous nonsolvents including a solution of 18% iodine/82% ethanol, ethanol, and water. The effect of these coagulants on the structure and mechanical properties of the PBZT fibers was studied. Structural and mechanical studies were performed on as-spun fibers. Wide-angle X-ray diffraction techniques have shown that fibers coagulated in the presence of iodine anions had d-spacings that were unique, as well as d-spacings that were characteristic of PBZT or iodine anions. Tensile and shear properties were highest in a fiber having a spin/draw ratio of 3 which contained 19.5% iodine species by weight. For these fibers, an average tensile strength of 2.2 GPa and a torsional modulus of 1.14 GPa was recorded. For fibers having this spin/draw ratio, and undergoing no post-processing heat treatment or tension drying, these values are much higher than would be expected.