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The tropics have a huge natural potential for the production of forage plants, many of which are valuable sources of nutrients for monogastric animals. This article attempts to review the work that has focused on the chemical composition of some of the most important tropical forages, including amino acid balance, and on evaluating the effects of preservation method and the effects of including these forages on the intake, diet digestibility and performance of growing pig and pregnant sows. The major green forages covered are cassava leaves (Manihot esculanta Crantz), groundnut foliage (Arachis hypogaea), sweet potato vines (Ipomoea batatas), leucaena leaves (Leuceana leucocephala), mungbean foliage (Phaseolus aureus), water spinach (Ipomoea aquatica Forsk), duckweed (Lemna minor) and Tricantera leaves (Trichantera gigantea). There is some evidence that green forages generally have an acceptable amino acid profile, but that for a variety of reasons, in particular the presence of anti-nutritional factors, including them in pig diets at high levels depresses digestibility and feed intake. Sun-drying and ensiling can be good preservation methods under tropical conditions that reduce the content of some anti-nutritional factors. There are differences in response to forage inclusion in diets for growing pigs, depending amongst other things, on the material that the forages replace. However, pregnant sows can utilize high fiber diets, and green forages can be a useful ingredient in diets for sows during pregnancy, as they not only are relatively high in protein but also in vitamins and minerals, and can give good reproductive performance.