As part of continuing studies on the genus Mochinea (Compositae), the isolation and identification of the sesquiterpene lactone dehydrocostus lactone (3) and a previously unknown naturally occurring pentacyclic triterpene, bauerenyl acetate (1), from the bark of Mochinea polymorpha (Less.) DC. are reported. Compound 1 was identified by comparison of its physical and chemical properties: alkaline hydrolysis of 1 yielded bauerenol, which was subsequently oxidized with Jones reagent to bauerenone (consistent with literature data for bauerenone, 4-6). The 13C NMR chemical shifts of compound 1 were assigned using model compounds and known substituent effects (7-11). Spectral data (IR, PMR, CMR, MS) for 1 are provided. The plant material was collected in Campinas, São Paulo, Brazil in December 1979. Extraction and isolation involved hexane extraction of dry powdered trunk bark (1.0 kg), silica gel chromatography of the crude extract, and CHCl3 elution to obtain bauerenyl acetate (1, 0.120 g, mp 290-292°C). Hydrolysis of 1 (30 mg) in 5% EtOH-KOH solution gave bauerenol (20 mg, mp 206-208°C), and oxidation of bauerenol with Jones reagent yielded bauerenone, identical to literature reports (4-6). Acknowledgments are made to those who provided plant classification, spectral data, authentic samples, and financial support (CNPq, CEPG, FINEP).