A field experiment using 2 patterns of irrigation and 1 level of nitrogen fertilizer (10 g-N m-2) was conducted in order to discern water and nitrogen interactions that may control production of creosotebush (Larrea tridentata (D.C.) Cov.). The 2 patterns of irrigation simulated precipitation from small, frequent events (6 mm water added weekly) or large, infrequent events (25 mm water added monthly). Understnaing the factors controlling the production of this rangeland shrub may aid in the development of strategies for management. Vegatative growth occurred mostly during March-May (spring) and August-October (summer-fall). Fruit production occurred mainly in the spring and root growth ocurred mainly in the summer-fall. Irrigation increased vegetative growth and decreased fruit produciton. Responses to irrigation were greater during summer-fall than in the spring. Small, frequent water additions caused larger increases in vegetative plus fruit growth than did large, infrequent water additions. Nitrogen fertilization increased the growth of both vegetation and fruit in irrigated and unirrigated plots. Stem mortality and root growth were not significantly affected by irrigation or nitrogen fertilizer. These results suggest that creosotebush production is limited by both soil moisture and nitrogen availability and that temporal patterns of rainfall may be as important as total amounts.