Bis(indole) alkaloids, of the topsentin class (1-4) and hamacanthin class (5-9), isolated from the marine sponge Spongosorites sp. were investigated using several biological assays. In the evaluation of antimicrobial activity against various strains of bacteria and fungi, compounds of the hamacanthin class exhibited more potent antibacterial activity than those of the topsentin class. Deoxytopsentin (1) and hamacanthin A (5) also exhibited significant antibacterial activity against methicillin-resistant Staphylococcus aureus, with MIC values of less than 12.5 microg/ml. In the antifungal activity test, hamacanthins, especially hamacanthin A (5), showed potent inhibitory activity against medically important pathogenic fungi. In contrast, all of the topsentins (1-4) were inactive against fungal growth. These compounds (1-9) also exhibited moderate cytotoxicity against cancer cell lines at concentrations between 1.1 and >20 microg/ml.