Two pyrrololactams, likely degradation products of more complex known guanidines, were isolated from several marine sponges [Hymeniacidon aldis and lissodendoryx]. 5-Bromo- and 4,5-dibromopyrrole-1-carboxylic acid methyl esters were also isolated. A complex guanidine metabolite, poorly soluble in DMSO [dimethyl sulfoxide], was found to give sharp, resproducible NMR spectra in acid media. [Implications with respect to the cytotoxic properties of these metabolites were presented.