The turtle Pseudemys scripta elegans hydroxylates nalidixic acid into 7-hydroxynalidixic acid; this latter metabolite is oxidised into 7-carboxynalidixic acid. The elimination half-life of nalidixic acid in the turtle is 30 h. No glucuronides of nalidixic- and 7-hydroxynalidixic acid are formed, as they are in man.