Résumé : The fast Fourier‐transform proton magnetic spectrum of Adenylyl‐uridine (ApU) was taken at 270 MHz. The complex group of signals due to the ribose protons could be analyzed to yield chemical shifts. 1H1H and 1H31P coupling constants. The assignment of the various peaks was based mainly on the known assignment of the N6‐monomethylated analogue m6ApU, see C. Altona et al., Nature 247, 558 (1974). Best values of the chemical shifts and coupling constants of ApU were obtained by carrying out a series of computer simulations of line shapes and intensities. Copyright © 1974 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim