Several studies have addressed the interaction between fatty acids and lipids with central nervous system peptides. Because aminopeptidases (AP) are involved in the regulation of neuropeptides, this work studies several AP expressed in cultured astroglia, after exogenous addition of oleic and linoleic fatty acids and cholesterol to the culture medium. Alanyl-AP, arginyl-AP, cystyl-AP, leucyl-AP, tyrosyl-AP and pyroglutamyl-AP activities were analysed in whole cells using the corresponding aminoacyl-beta-naphthylamides as substrates. Oleic acid inhibits alanyl-AP, cystyl-AP and leucyl-AP activities, whereas linoleic acid inhibits alanyl-AP, arginyl-AP and tyrosyl-AP activities. Neither oleic acid nor linoleic acid modifies pyroglutamyl-AP activity. In contrast, cholesterol increases arginyl-AP, cystyl-AP, leucyl-AP, tyrosyl-AP and pyroglutamyl-AP activities, although it does not modify alanyl-AP activity. The changes reported here suggest that oleic and linoleic fatty acids and cholesterol can modulate peptide activities via their degradation route involving aminopeptidases; each of them being differentially regulated.