ABSTRACT.Intestinal absorption of macromolecules, using human α‐lactalbumin (α‐LA) as a marker, was studied in breast‐fed and formula‐fed infants with infantile colic. Serum samples taken at 30 and 60 min after an intake of human milk were analyzed for α‐LA by a competitive radioimmunoassay technique. Breast‐fed infants with infantile colic had significantly higher s‐α‐LA levels compared with age‐matched breast‐fed control infants 0‐1 month of age: median value 926 μg α‐LA/I serum/I human milk/kg bodyweight (n= 11) versus 150 (n= 34); 1–2 months of age: 173 (n= 22) versus 31 (n= 16); 2–3 months of age: 132 (n= 8) versus 11 (n= 16). Similarly, formula‐fed colicky infants had significantly higher s‐α‐LA levels than agematched formula‐fed control infants 1‐2 months of age: median value 126 (n= 12) versus<10 (n= 14); 2–3 months of age: 156 (n= 11) versus<10 (n= 10). The increased absorption of the macromolecule human α‐lactalbumin in infantile colic suggests that the gut m