The functional response of the phytoseiid predator Chileseius camposi González y Schuster, 1962 (Acarina:Phytoseiidae) on densities of its prey Panonychus ulmi (Koch, 1836) was evaluated under controlled temperature (20 ± 2 ºC),, relative humidity (75 ± 15%) and photoperiod (16:8h L:D). A functional type II response was displayed (Holling s disk). Holling, Wolf transformation and Rogers models gave similar values for estimating parameters of the Holling s disk equation; however, estimates produced by the Livdahl and Stiven model were higher. Values of attack rate and handling time can be considered within the normal range for phytoseiid generalists. Rev. Biol. Trop. 56 (3): 1255-1260. Epub 2008 September 30.