A total of 6,618 calves fed at eight Iowa feedlots were used to evaluate the effect of postweaning health on feedlot gain and carcass quality grade. The calves, representing 12 states, were consigned to the Iowa Tri-County Steer Carcass Futurity and were weighed upon arrival, after 35 days, at reimplant, and prior to harvest. A common dietary energy level was utilized at each feedlot. Calf health was classified as no treatment (NT; N=5,500), single treatment (ST; N=575), or two or more treatments (2T; N=543). The predominant cause of treatment was respiratory problems. Calves were sorted and harvested when they were visually evaluated to have 0.4 inches of fat cover. Feedlot ADG was 3.06, 2.93, and 2.87 lb/day for the NT, ST, and 2T calves, respectively. Calf sex, origin of calf (Southeast vs. Midwest), season of delivery (fall vs. spring), and color (black vs. red vs. white) all affected feedlot gain. The percent USDA Prime, Choice, Select, and standard for NT, ST, and 2T calf carcasses were 1.87, 70.3, 25.3, and 2.6; 1.05, 62.9, 30.1, and 5.9; and 0.9, 57.9, 30.6, and 10.6, respectively. A total of 4,499 calves were Angus-type calves eligible for Certified Angus Beef® (CAB®) acceptance. CAB® acceptance percentages for NT, ST, and 2T carcasses were 27.1, 24.2, and 18.7, respectively. CAB®acceptance rates were also impacted by calf sex (steers = 14.7% vs. heifers = 23.7%) and season of feedlot delivery (spring = 14.5% vs. fall/winter = 23.8%). Calves treated two or more times upon feedlot arrival had reduced feedlot gain, reduced quality grade, and reduced CAB® acceptance rate compared to untreated calves.