Two new indolocarbazole alkaloids, 7-oxo-3,8,9-trihydroxystaurosporine (1) and 7-oxo-8,9-dihydroxy-4'-N-demethylstaurosporine (2), were isolated from samples of the marine ascidian Cystodytes solitus. Their structures were determined by a combination of spectroscopic techniques, including (+)-HRMALDITOFMS and 1D and 2D NMR spectroscopy, and comparison with published data for related structures. Both compounds displayed strong cytotoxicity against three human tumor cell lines.