The activity of muscle aminopeptidases (alanyl, arginyl, leucyl and pyroglutamyl aminopeptidases) have been assayed along the processing of dry-cured ham. The generation of free amino acids resulting from aminopeptidase action on N-terminal of proteins and peptides has been also analyzed. The assayed aminopeptidases, except pyroglutamyl aminopeptidase, showed good stability. Alanyl and arginyl aminopeptidases have optimal neutral pH near the pH in ham and, in addition, their spectrum of activity against terminal amino acids is in coincidence with the observed release of free amino acids in ham. So, both aminopeptidases appear to be the main contributors to the generation of free amino acids during the processing of dry-cured ham. (C) 2000 Elsevier Science Ltd. All rights reserved.