Four-week-old male chickens were subjected to one of the following treatments: 0 ppm mercury (Hg) plus water ad libitum, 0 ppm Hg plus limited water (LW), 500 ppm Hg plus water ad libitum, and 500 ppm Hg plus LW. Exposure was for each of the following time intervals: 0-3, 0-6, 0-9, 0-12, and 0-15 d. LW significantly increased red blood cell (RBC) numbers, hematocrit (HCT), mean corpuscular volume (MCV), and hemoglobin (Hb) level and significantly decreased mean corpuscular hemoglobin (MCH) level within 3 d of treatment. Mercury produced variable results, with no significant trends developing during the treatment period. The effects caused by Hg appeared to be masked by the effects of dehydration. The birds receiving water ad libitum had numerically greater RBC numbers and HCT and Hb levels than birds receiving water ad libitum that was contaminated with Hg, while the effects caused by Hg in the groups that received limited water were not consistent. Each group was given a recovery period of 14 d, during which time all birds received uncontaminated water and feed ad libitum. The hematologic effects caused by Hg and water deprivation did not return to a normal condition. Reduced RBC numbers, HCT, and Hb levels were observed at the end of the recovery period in the birds that were exposed to Hg and/or water deprivation.