An account is given of the chemistry and phytobenthos of streams in the vicinity of two old lead mines in the Hautes-Pyrénées south of Lourdes. All of the nine sites studied had elevated levels of aqueous Zn, and also in most cases of Cd and Pb. There was some evidence that increasing levels of heavy metals led to a decreased flora, but 30 species were recorded at sites with > 10 mg l-1 Zn. The most restricted flora occurred at a site with a conspicuous white precipitate, consisting largely of anglesite; here only three species were present: Schizothrix sp., Pohlia cruda, Solenostoma crenulatum.