Interactions between HPA (Hypothalamic-pituitary-axis) and immune system seem to involve the EPO (endogenous opioid peptides) system, as shown by some recent findings. Possible relationships between beta-endorphin (beta-End) synthesis and severity rate of immunodeficiency have been studied in 48 HIV Ab positive patients, at different stages of infection. A statistically significant decrease in the beta-End synthesis was observed in these patients, as compared to a control group of 19 healthy subjects, but this decrease was not related to the CD4+T lymphocytes number. Plasmatic levels modifications of HPA-related peptides were not observed in the IVC1 CDC group.