AbstractDisplacements of1H‐NMR chemical shifs for caffeine in D2O solution as a function of concentration conform to the behaviour expected for pure dimer formation according to the equilibrium 2(caffeine)⇄(caffeine)2with a statistical probability of at least 95%. Confidence limits reported earlier for the dimerisation constant of caffeine represent the real statistical dispersion in the experimental data and do not reflect a systematic error such as tetramer format