Four new compounds, belonging to the tetranortriterpenoid family, named dysoxylins A-D (1-4), isolated from Dysoxylum gaudichaudianum, were found to exhibit potent antiviral activity against respiratory syncytial virus (RSV). These structures were determined by NMR spectroscopy and mass spectrometry and were shown to have anti-RSV EC50 activities in the range 1.0-4.0 microg/mL in cytopathic effect inhibition and plaque reduction assays.