We have compared barium swallow with a radionuclide gastro-oesophageal scintigraphy (milk scan) method of detecting gastro-oesophageal reflux in 26 infants. In 17 cases, presenting as near miss sudden infant death syndrome, reflux was detected in 2 by barium swallow and in 8 by scintigraphy. In the remaining 9 infants with suspected pulmonary aspiration, reflux was demonstrated by barium swallow in 2 and by scintigraphy in four. Aspiration after gastro-oesophageal reflux was demonstrated only by the radionuclide scan. The feasibility of recording physiological variables during periods of reflux was confirmed.