Two novel polyoxygenated steroids, incrustasterol A (1) and B (2), have been isolated from the marine sponge Dysidea incrustans, collected in the Mediterranean sea along the coasts of Tunisia. The structures, which include a rare Δ8(9), 11-keto functionality along with other oxygenated functions on the rings A and B, were determined by interpretation of spectral data. These steroids were cytotoxic against human non-small-cell lung, renal and melanoma carcinoma cell lines.