Byssal threads are tough collagenous fibers that mussels use to secure themselves. against dislodgement by waves in the marine intertidal zone. Here, preCol, a family of hybrid collagens comprising up to 96% of the protein content in certain regions of byssal threads, was purified in mg amounts from mussel foot tissue for the first time. Conditions for drawing preCols into quality fibers ex vivo were investigated. The most important factor affecting fiber formation was the pH of the drawing solution. The morphology and tensile properties of drawn fibers were also characterized and suggest that a liquid crystal mesophase combined with cross-linking by His-metal coordination plays a role in the assembly/mechanics of drawn fibers and likely in native byssal threads as well.