Although higher plants represent a significant portion of the total biomass in some aquatic environments, their use in ecosystem evaluation has lagged behind that of other organisms. This is partly due to a lack of convenient aquatic higher plant systems that can be employed for ecotoxicological assessment. However, the aquatic C-3 monocot Lemna gibba has many attributes that makes it useful for ecosystem health assessment. In this report, using examples from the literature and our research, some of the applications Lemna has for environmental research are discussed. Toxicant impacts on Lemna can be readily assessed in terms of growth; the plants multiply quickly and changes in biomass (which doubles approximately every 2 days) can be accurately measured by counting leaves. The plants are small, allowing for simultaneous multiple replication. The small size also makes the lighting conditions easy to control; sunlight can be accurately simulated and specific spectral regions can be enhanced or deleted. Lemna is amenable to in vivo chlorophyll and photosynthesis assays, which make excellent companion endpoints for growth. The plants assimilate chemicals directly from the growth medium, facilitating controlled toxicant application. Furthermore, Lernna has a high bioconcentration capacity, indicating a potential for use in bioremediation technologies.