The relationship between the fibrillation and swelling of lyocell fibers(spun by N-metyl-morpholine N-oxide systems) was studied by varying the spinning conditions such as degree of polymerization($DP_{w}$), cellulose concentration, and draft ratio. The fibers, treated by constant stirring with stainless balls in the wet and dry state, exhibited a increase in the fibrillation index with increase in $DP_{w}$, cellulose concentration, and draft ratio. The decrease in wide angle X-ray scattering intensity with water swelling suggests that the less-ordered cellulose in and between the crystals take up water. The increase in fibrillation index correlates I inverse proportion to swelling.