In many applications of NMR spectroscopy to chemistry, quantitation play s a key role. This paper argues that peak heights not only can be used for quantitative work in NMR but that for careful work they should be used. Integrals are accurate, but because they depend on many subjective factors, their precision is suspect. Peak heights are very reproducible on modern spectrometers and so, given this precision, the accuracy can be obtained as well by using calibration methods. An example of the application of these methods is given in the case of a 13C labelling experiment that elucidates a photochemical transformation. Key words: NMR, labelling, quantitation, peak heights, integrals.