Two novel epimeric compounds, viminadione A (1) and viminadione B (2), have been isolated by bioassay guided fractionation of the aerial parts of Callistemon viminalis and their structures (including relative stereochemistry at C-7, C-8, and C-9) elucidated by spectroscopic methods. Viminadione A (1) exhibits moderate insecticidal activity in comparison with natural pyrethrum extract. Viminadione B (2) is less active.