Recently we reported the isolation of three highly functionalized pyrroloquinoline alkaloids, batzellines A (1), B (2), and C (3), from the deep water Caribbean sponge Batzella sp. (family Esperiopsidae, order Poecilosclerida). The structure of batzelline A was secured by X-ray analysis. Further search for bioactive agents from Batzella has resulted in the discovery of four structurally related pyrroloquinolines, which we have named isobatzellines A (4), B (5), C (6), and D (7). The isobatzellines were found to exhibit in vitro cytotoxicity against P388 leukemia cell and moderate antifungal activity against Candida albicans. The structures of the isobatzellines are described here and are based on spectral comparison with batzelline A and chemical interconversion.