molecules, 1 supramolecular chemistry and host/guest interactions, and biomolecular function and interactions. By using rf pulses to perturb the magnetisation of systems in dynamic equilibrium, the associated chemical exchange processes can be characterised with high precision across a wide range of timescales. A variety of experiments have been developed towards this end, including NOESY (also referred to in this context as EXSY), ZZ-exchange spectroscopy, chemical exchange saturation transfer (CEST), and CPMG/R 1ρ relaxation dispersion. All of the above experiments are based on the characterisation of exchange occurring during a specific mixing time within the pulse sequence. However, resonance lineshapes are also directly sensitive to chemical exchange processes, provided that the exchange rate, kex, is within one or two orders of magnitude of the frequency difference, ∆ω, between the exchanging resonances. Therefore, in a long-standing approach termed lineshape analysis or 'dynamic NMR', one-dimensional (1D) spectra may be fitted in a least-squares sense to solutions of the Bloch-McConnell or Liouville-von Neumann equations that govern the evolution of magnetisation, in order to characterise the chemical exchange process. The approach has also been extended to two-dimensional (2D) lineshape analysis: the fitting of 2D NMR spectra, by direct simulation of the relevant pulse sequence. This approach, and the associated TITAN analysis software, has since found applications to a variety of biomolecular interactions. As part of an effort to validate the accuracy of 2D lineshape analysis, we acquired a series of measurements of the small molecule N ,N -dimethyl-trichloroacetamide (DMTCA) (Fig. ), the two methyl groups of which undergo exchange by rotation about the amide bond with a rate of 125 s -1 at 298 K. DMTCA is a simple molecule, with no resolved homonuclear scalar couplings, but serves to illustrate fundamental principles that will be equally applicable to more complex molecules and exchange processes.