SUMMARY: The ovaries of the lungfish (Protopterus annectens Owen) were examined for sex steroids. Extracts produced a positive response in the mouse uterine weight test. Processing by paper chromatographic methods indicated the presence of oestriol, oestrone, a trace of oestradiol-17β and progesterone, but not enough material was available for their definitive chemical demonstration. The possible significance of these results is discussed.