Endocrine and immune parameters, namely glucocorticoid receptors (GcR) and IFN-γ production in peripheral blood mononuclear cells (PBMC), and corticosterone in plasma, were studied in groups of four male rabbits observed in seminatural conditions in relation to agonistic behaviour and to seasonal variations. These parameters were selected on the basis of the findings that the presence of GcR in PBMC gives an indication of the in vivo biological effects of glucocorticoids and that PBMC cytokine production and plasma corticosterone are related to social behaviour. The frequency of active and passive behaviours was used to rank the animals. Seasonal variations were present for agonistic behaviours (Attack, Follow, Chase) and for plasma corticosterone, which were significantly higher in winter. IFN-γ production in PBMC was increased after social interactions in both seasons, while plasma corticosterone was increased only in winter. GcR capacity in PBMC was decreased after social interactions. The results indicate that social and physical environmental factors are correlated with immune-endocrine functions.