Three new prenylflavones, KB-1 (1), KB-2 (2) and KB-3(3) have been isolated from Indonesian Artocarpus communis FORST. The structures of these flavones were determine by analyses of their 1H-and 13C-NMR spectra including HMBC technique. All these compounds exhibited strong cytotoxic activities against leukemia cells (L-1210) in tissue culture