• Twenty-five children with chronic constipation underwent serial monitoring of serum β-carotene, retinol (vitamin A1), and α-tocopherol (vitamin E) levels during mineral oil therapy. Mineral oil was administered between meals. Patients were monitored for up to four months of therapy. Mean serum β-carotene levels fell from 1.0±0.5 μmol/L (55.7±26.0 μg/dL) to 0.7±0.4 μmol/L (35.9±22.1 μg/dL) after the first month of mineral oil therapy and remained depressed throughout the remainder of the study. Serum α-tocopherol levels remained unchanged throughout the observation period. There was a modest increase in serum retinol levels during the study, especially after three months (from 1.48±0.84 μmol/L [42.3±24.1 μg/dL] to 2.22±0.77 μmol/L [63.5±22.1 μg/dL]). We conclude that while a short course of mineral oil can induce a reduction in the serum level of β-carotene, the treatment has no adverse effect on serum levels of retinol and α-tocopherol.