PURPOSE To analyze the amount of gadopentetate dimeglumine excreted into human breast milk following intravenous injection of a clinical dose. MATERIALS AND METHODS Gadopentetate dimeglumine was injected intravenously in 20 lactating women (23-38 years of age). Breast-feeding was interrupted for at least 24 hours. Serial samples of expressed milk were collected and analyzed for gadolinium concentration by means of inductively coupled plasma atomic emission spectrometry at a wavelength of 342.247 nm. RESULTS The cumulative amount of gadolinium excreted in human breast milk during 24 hours was 0.57 micromol +/- 0.71 (SD; range, 0.05-3.0 micromol). The excreted dose was thus less than 0.04% of the administered intravenous dose (range, 0.001%-0.04%; mean, 0.009% +/- 0.010) for all cases. CONCLUSION Less than 0.04% of administered gadopentetate dimeglumine is excreted into human breast milk. The amount transferred to a nursing infant orally would be far more than 100 times less than the permitted intravenous dose (200 micromol per kilogram of body weight) for neonates. The recommendation of a 24-hour suspension of breast-feeding for lactating women should thus be reconsidered.