At birth, the pair 1 infant weighed 3.3 kg and had a gestational age of 37 weeks. The pair 2 infant weighed 3.9 kg and had a gestational age of 38 weeks at birth. Both infants received breast milk exclusively during their first 6 months. The pair 1 mother began taking venlafaxine (75 mg/day) on the day of delivery, while the pair 2 mother took the medication (150 mg/day) throughout her pregnancy. The pair 1 infant was 3 weeks old and weighed 4.1 kg when the serum testing was performed; the pair 2 infant was 4 weeks old and weighed 4.6 kg. The interval between the time the mother took her oral dose and blood was drawn for serum testing was 3.0 hours for pair 1 and 2.0 hours for pair 2. The mothers’ serum medication concentrations were 31.00 and 28.00 ng/ml, respectively, and their serum metabolite concentrations were 148.00 and 230.00 ng/ml. Venlafaxine was not detectable in either infant (0.00 ng/ml in both infants), but the metabolite was present in both children: pair 1 infant, 16.00 ng/ml; pair 2 infant, 21.00 ng/ml. No adverse sequelae, such as changes in sleep, feeding patterns, or behavior, occurred in the infants, as shown by maternal reports and review of pediatric records. In addition, the pediatric records indicated that the children’s weight and heights were in the 85th–100th percentiles.