Commercially grown Virginia and Burley tobacco (grown in North Carolina) were sampled at different time points during development, harvesting and curing to assess biochemical and metabolic changes. The aim was to provide information relating to the timing and build up of specific compounds in tobacco throughout growth and curing. These samples were used to generate a profile of the amino acid content of both tobacco types at harvest through to the final cured material, and demonstrated a striking difference between the two types. This is likely to be due partly to varietal differences but most probably a consequence of the very different nature of the flue-curing and air-curing processes. In Virginia tobacco there was a large increase in proline and histidine content which may occur in response to stress. Proline levels have been reported to rise dramatically in other plants, in particular to water stress and can make up to 80% of the amino acid content under certain conditions (Chen and Dickman, 2005, PNAS(102):3459-3464). The fact that flue-curing is a rapid process carried out at high temperatures which acts to fix the tissue, explains why the proline content remained high. The main nitrogen storage amino acids, asparagine and glutamine also increased during the initial stages of flue-curing. During air-curing the leaves are metabolically active for a longer period of time, proline and histidine levels were high at the start of air-curing but then decreased to a less significant level by the end of the cure. Increases in asparagine, aspartate and alanine content were also observed. This data provides an important insight into the composition of cured tobacco leaves and offers some indication of the amino acids which potentially contribute to the distinctive properties of either Virginia or Burley tobaccos.