Percutaneous respiration was studied in 27 newborn infants (birth weight 0.96 to 4.43 kg, gestation 27 to 40 weeks) using a closed skin cell attached to the upper abdomen into which saturated air at 37 degrees C was introduced. Gas exchange across the skin was found to be strongly related to gestational age. Term infants had lower rates of gas exchange than found across adult skin (mean O2 absorption 32.0 vs 62.0 ml/m2/hr, mean CO2 excretion 40.5 vs 86.5 ml/m2/hr). In the first few days of life infants of less than 31 weeks gestation had rates of gas exchange five to six times higher (mean O2 absorption 178.4 ml/m2/hr, mean CO2 excretion 214.8 ml/m2/hr) than those in term infants, but these fell rapidly toward term levels by 2 weeks of age. Gas exchange correlated well with skin water loss, suggesting that the epidermal barrier limits both processes. There was a linear increase in skin O2 absorption as the O2 concentration in the skin cell increased. We estimate that if in the early neonatal period an infant of less than 31 weeks gestation were nursed naked in 40% oxygen, about 13% of total resting oxygen requirements could be obtained through the skin. Under certain limited circumstances, percutaneous oxygen delivery might be clinically useful.