The chemical investigation of Pseudoceratina sp. led to the isolation of six compounds including tyrosine brominated isoxazoline alkaloids (1 and 2), polyketide (3), and 5 alpha,8 alpha-epidioxysterols (4-6). The structures of these compounds were identified by comparison of NMR and MS spectroscopic data with those previously reported. Compounds 3-6 were isolated for the first time from sponges of the genus Pseudoceratina. The chemotaxonomic significance of these compounds was discussed.