This study was conducted to assess the effects of caffeine on the dam and the physical development of rat offspring. Pregnant Sprague-Dawley rats (20 per dose group) were administered caffeine by gavage at 0 (control), 5, 20, and 80 mg/kg body weight (bw) daily from gestational day 6 through lactation using caffeine dissolved in water. The developmental toxicity of caffeine was evaluated. Dams in the 80 mg/kg bw group exhibited splenic atrophy.