Thirty Boer and 27 Kiko does were exposed to Spanish bucks and evaluated for doe reproduction, pre-weaning kid growth, and production efficiency in the humid, subtropical south-eastern United States. Does of each breed were represented by at least seven seed stock farms and eight sires. Twenty-five Boer and 23 Kiko does gave birth to at least one live kid. Body weights at parturition were heavier for Boer than Kiko dams. Litter size and litter weight were similar at birth for Boer (1.92 Â± 0.12 kids, 6.05 Â± 0.31 kg) and Kiko dams (1.82 Â± 0.12 kids, 5.90 Â± 0.33 kg). Birth weights were similar between 46 Boer and 42 Kiko F1 kids. Birth weights were heavier for single than for twin kids; twin kids were heavier at birth than triplet kids. Bucks were heavier than does at birth. At least one kid was reared to weaning by 20 Boer and 21 Kiko dams. Body weights at weaning were similar for dam breeds. Litter size, litter weight, and litter weight to doe weight ratio were significantly greater for Kiko (1.85 Â± 0.09 kids, 31.73 Â± 1.52 kg, 78.1 Â± 4%) compared with Boer dams (1.58 Â± 0.09 kids, 26.48 Â± 1.51 kg, 63.9 Â± 4%) at weaning. Pre-weaning growth rates and weaning weights were greater for 38 Kiko compared with 32 Boer F1 kids and were greater for bucks than for does. Kiko F1 kids had significantly lower attrition rates (9.5%) and Kiko does had significantly fewer episodes of lameness (1.60 Â± 0.33 episodes/doe) compared with Boer (34.8%, 3.31 Â± 0.31 episodes/doe). Kiko dams tended to wean a higher kid crop percentage and weaned higher litter weights per doe exposed compared with Boer dams. Significant variation existed between Boer and Kiko as maternal breeds for performance, efficiency, and fitness under these research conditions.