The photosynthetic capacities of three species of dodder, largeseed dodder (Cuscuta indecora, Choisy), field dodder (Cuscuta campestris, Yuncker), and small-seeded dodder (Cuscuta approximata, Bab.) were studied by radioactive carbon dioxide uptake in light and darkness, and by manometric methods. Both methods showed that all three species were able to carry on a small amount of photosynthesis. The photosynthetic capacity was highest in the seedling, and decreased as the dodder became parasitic.