Three new scalarane sesterterpenoids-hyrtiolide (1), 16-hydroxyscalarolide (2), and 12-deacetyl-Delta(17)-hyrtial (3), were isolated from Okinawan sponge Hyrtios erectus, along with scalarolide (4) and 12-deacetylhyrtial (5). The structures of new compounds 1-3 were determined by spectroscopic analysis and chemical conversions. Compounds 3 and 5 showed antiproliferative activity toward KB cells.