Among the four cultivated species of Gossypium, diploid species (G. herbaceum and G. arboreum) are generally cultivated in marginal, drought prone environments of Asia due to their inherent ability to withstand drought. Diploid cottons are also known for their ability to resist sucking pests such as hoppers, white flies, thrips and aphids, and leaf curl virus. Before the spread of G. hirsutum in Asia, diploids were grown widely, but gradually replaced due to short, coarse and weak fiber and undesirable boll and plant features. These are still cultivated in traditional cotton growing areas of India, Pakistan, China, Bangladesh and Iran. India has structured genetic improvement programs aiming to improve yield potential and fiber quality of diploids. World germplasm collections are preserved in India, however, small sets of local/imported collections are also maintained in France, USA, China, and Iran. G. herbaceum has contributed the A-genome to tetraploid (AADD) cotton and is important to studying evolution of cultivated cotton and fiber related genes. The origin, evolution and distribution of A-genome diploids have been presented in this chapter along with different local types available in India. Compiled information on these important gene pools of cotton is seldom found in the literature. We made efforts to assemble valuable information on breeding efforts made in developing new genotypes or biotechnologically important diploid cotton populations.