Root distribution can be influenced by many soil and environmental factors in addition to the influence of genetics and environment on crop morphology and plant vigor. In semi-arid and arid environments, soil water availability during much of the growing season in largely determined by irrigation practices once limited water from rainfall is depleted. Some irrigation methods attempt to apply water uniformly across the entire soil surface area (solid-set sprinklers, dead-level basin, border checks). Others (furrow, drip) apply the water to a more limited portion of the soil, after which some redistribution and lateral movement of water can occur. A three-year study was initiated under subsurface drip and furrow irrigation in cotton to evaluate the influence of time of growing season, irrigation method, and amount applied per irrigation on root length density (RLD) and distribution within the soil profile. Furrow irrigated plots receiving full irrigation had RLD values significantly lower than SDI plots in within-plant row cores, but significantly higher values within cores from the furrow area. Under full (100% ETc) irrigation, the root system of the SDI plots was more concentrated (higher RLD and root mass) near the emitter (within 35 to 45 cm) than near the surface or at greater depths or distances from the emitter. Lint yields in all treatments were good to excellent, exceeding 1700 kg lint/ha.