Four new alkaloids isariotins G-J (1-4), together with the known isariotins, were isolated from cultures of the Lepidoptera pathogenic fungus Isaria tenuipes. The structures were elucidated on the basis of NMR spectroscopic and mass spectrometry data. Compounds 1-4 exhibited antimalarial and cytotoxic activities. © 2011 Phytochemical Society of Europe.