In the present study we report on the identification of two novel microsomal metabolites of the investigational anticancer agent Sprigermanium (NSC-192965). The two metabolites were isolated after incubation of Spirogermanium with fortified rat liver microsomes. Mass spectrometry studies indicate that one of them, formed in major quantities, is hydroxy Spirogermanium. The other metabolite appears to correspond to bis-desmethylated Spirogermanium.