The effect of daily forced swimming (15 min) of rats for 21 consecutive days on peripheral-type bentodiazepine receptors (PBR) was investigated. A significant reduction (–17%; p < 0.05) was observed in renal PBR in the stressed animals. A nonsignificant reduction of –18% was detected in adrenal PBR. The maximal binding capacity of [3H]PK 11195 was unaltered in the liver, heart, testis and thymus. It seems that the kidney is especially sensitive to repeated stress. The renal PBR reduction may be related to habituation to stress, and may reflect an adaptatory mechanism aimed at preventing long-term stress-induced overactivity of the reninangiotensin sys