The deformation mechanics of dry networks of large-aspect-ratio fibers with random orientation controls the processing of long-fiber thermoplastics (LFTs) and greatly affects the mechanical properties of the final composites. Here, we generate initial geometries of fiber networks in a cubic unit cell with a fiber aspect ratio of lid =100 and fully periodic boundary conditions for later numerical simulation. The irreversible random sequential adsorption (RSA) process is first used to generate a quasi-random structure due to the excluded-volume requirements. In order to investigate the nonequilibrium character of the RSA, a second method, which is similar to the mechanical contraction method (MCM) (Williams and Philipse, 2003, "Random Packings of Spheres and Spherocylinders Simulated by Mechanical Contraction," Phys, Rev, E, 67, pp. 1-9) and based on a simplified Metropolis Monte Carlo (MC) simulation is then developed to produce quasiequilibrium fiber geometries. The RSA packing results (4>K4.423% when using a fiber aspect ratio of ¡00) are in good agreement with the maximum unforced random packing limits (Evans and Gibson, 1986, "Prediction of the Maximum Packing Eraction Achievable in Randomly Oriented " Compos. Sei. TechnoL, 25,. The fiber structures were characterized by several distribution functions, including pair-spatial and pair-orientation distributions, based on either the center-tocenter distance or the shortest distance between the particles. The results show that the structures generated by the RSA have an easily-detectable long-range spatial correlation but very little orientational correlation. In contrast, the quasi-equilibrium structures have reduced spatial correlation but increased short-range orientational correlation