We report here the results of the analysis of aromatase and steroidogenic factor 1 expression in adult lung of the urodele amphibian Pleurodeles waltl. By RT-PCR experiments, we show the expression of the estrogen synthesizing enzyme, aromatase, in this organ. In the lung, no significant difference between males and females was observed in the level of aromatase mRNAs. Aromatase mRNA levels were also identical to those found in the brain but it was 2-fold lower than in the testis or the ovary. Aromatase activity measurements reveal the presence of an active form of aromatase in the lung, which is similar in males and females. There is no difference in the level of aromatase activity between lung, brain and testis but a higher activity is measured in the ovary (13.7 fold compared with testis). So, the differences in aromatase mRNA level between the ovary and the other organs do not mirror the differences in aromatase activity, suggesting the involvement of post-translational events. Aromatase is also expressed in the lung of the anuran amphibian Xenopus laevis. In Pleurodeles lung, steroidogenic factor 1 mRNAs are also detected. There is no difference between males and females in the level of these mRNAs. The latter was not significantly different from those measured in the brain but a significant 2.1 fold higher level of expression was found in the gonads. These results demonstrate clearly the expression of steroidogenic markers in the adult lung of amphibians, with the biological significance of this remaining to be determined.