Available nitrogen contents in biologically aged wine were lower than in young (unaged) wine; this resulted in aslightly lower acetification rate and production with the former. The nitrogen composition of the two vinegars was very similar, with l-proline and l-cysteine as the major amino acids. By exception, only the vinegar from the young wine contained ammonium ion. The ageing process by flor yeast produces urea which is eliminated by the bacteria in the next stage.