The possible mechanism of inhalation anesthetics on the internal auditory impairment of the rat was investigated by determining the effect of nitrous oxide (N20) and isoflurane on the total RNA yield from the cochlea of the rats. Thirty healthy Wistar rats were randomly divided into 3 groups: group C (control group, n=10) with a 3-h unremitting inhalation of 50% O2 group N (ex-periment group, n= 10) with a continuous inhalation of 50% N2O+50% O2for 3 h, and group I (ex-periment group, n=10) with a 3-h sustained inhalation of 2.5% isoflurane. The TRIzol in combination with RNeasy was used to respectively extract the total RNA from cochlea of rats in the 3 groups. Spectrophotometry was used to detect total RNA yield and electrophoresis to detect the quality. The total RNA extracted from the cochlea of the rats in the groups C and N was 7.69 and 6.51 μg, respec- tively. There was a 15% decrease in the N group as compared with group C. The total RNA from the rats in the group I was 7.32 μg, and there was hardly any change in the group as compared with the group C. The value of A260/A280 in groups C, N and I was 2.07, 2.04 and 2.04, respectively, showing a very high RNA purity. The result of gel electrophoresis suggested that there was no degradation in the total RNA. It was suggested that the interference of N2O on the cochlear RNA yield might be one of the reasons which cause an injury of the ear. The isoflurane shows no harm on the heating.