In a previous study we have provided evidence, that acute experimental hypercapnia due to hypoventilation in the rabbit alters blood-cerebrospinal fluid barrier function in the brain (Pakulski et al. 1998). The purpose of this study therefore was to determine if lidocaine would prevent the observed alterations in the blood-cerebrospinal fluid barrier function. The experiments were conducted in 16 adult Chinchilla rabbits submitted to acute hypercapnia due to mechanical hypoventilation (PaCO2 between 8 - 9.5 kPa over 180 minutes) under pentobarbital anaesthesia. The studied group (n = 8) was treated by lidocaine infusion 10 mg kg-1 h -1. After 180 minutes of hypercapnia the value of cerebrospinal fluid-blood index of gentamycin concentration, indicating the permeability of the blood-cerebrospinal fluid barrier, was significantly lower in animals treated with lidocaine (4.03 2.32 vs. 19.05 5.49; P< 0.01). We conclude that lidocaine may attenuate the increase of blood-cerebrospinal fluid barrier permeability under conditions of experimental acute hypercapnia lasting 180 minutes in the mechanically ventilated rabbit.