American Journal of Primatology 68:245–256 (2006) RESEARCH ARTICLE Positive Reinforcement Training Affects Hematologic and Serum Chemistry Values in Captive Chimpanzees (Pan troglodytes) SUSAN P. LAMBETH 1Ã , JANN HAU 2, 3 , JAINE E. PERLMAN 1 , MICHELE MARTINO 1 , AND STEVEN J. SCHAPIRO 1 1 Michale E. Keeling Center for Comparative Medicine and Research, Department of Veterinary Sciences, University of Texas M. D. Anderson Cancer Center, Bastrop, Texas 2 Department of Experimental Medicine, University of Copenhagen, Copenhagen, Denmark 3 Department of Neuroscience, Uppsala University, Uppsala, Sweden Positive reinforcement training (PRT) techniques have received con- siderable attention for their stress reduction potential in the behavioral management of captive nonhuman primates. However, few published empirical studies have provided physiological data to support this position. To address this issue, PRT techniques were used to train chimpanzees (Pan troglodytes) to voluntarily present a leg for an intramuscular (IM) injection of anesthetic. Hematology and serum chemistry profiles were collected from healthy chimpanzees (n 5 128) of both sexes and various ages during their routine annual physical examinations over a 7-year period. Specific variables potentially indica- tive of acute stress (i.e., total white blood cell (WBC) counts, absolute segmented neutrophils (SEG), glucose (GLU) levels, and hematocrit (HCT) levels) were analyzed to determine whether the method used to administer the anesthetic (voluntary present for injection vs. involuntary injection) affected the physiological parameters. Subjects that voluntarily presented for an anesthetic injection had significantly lower mean total WBC counts, SEG, and GLU levels than subjects that were involuntarily anesthetized by more traditional means. Within-subjects analyses revealed the same pattern of results. This is one of the first data sets to objectively demonstrate that PRT for voluntary presentation of IM injections of anesthetic can significantly affect some of the physiological measures correlated with stress responses to chemical restraint in captive chimpanzees. Am. J. Primatol. 68:245–256, 2006.  c 2006 Wiley-Liss, Inc. Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/20148 Received 14 December 2004; revised 10 June 2005; revision accepted 20 June 2005 Contract grant sponsor: National Institutes of Health/National Center for Research Resources; Contract grant number: U42 RR15090; Contract grant sponsor: National Institutes of Health/ National Heart, Lung and Blood Institute; Contract grant number: N02-OR-0-4021. Ã Correspondence to: Susan P. Lambeth, Michale E. Keeling Center for Comparative Medicine and Research, Department of Veterinary Sciences, University of Texas M. D. Anderson Cancer Center, 650 Cool Water Drive, Bastrop, TX 78602. E-mail: slambeth@mdanderson.org r r 2006 Wiley-Liss, Inc.