Upland cotton, G. hirsutum, is a tetraploid (AADD) that has become the predominant cotton species of commerce worldwide. Bottlenecks during speciation and domestication have resulted in limited genetic diversity among upland cotton cultivars. In the summer of 2006 we crossed three upland cotton cultivars in a factorial design with one accession of G. armourianum and three accessions of G. thurberi. The upland cultivars were grown in a field and flowers were emasculated in the morning prior to pollen dehiscence (dawn until about 9:30 a.m.). These AADD/DD crosses are an initial step towards introgression of novel D-genome genes into upland cotton. In addition, doubling the chromosome numbers of the ADD triploid hybrids yields hexaploids that are also useful as bridging lines for introgressing genes from the A-genome diploid species. From 31 G. hirsutum/G. armourianum crosses, 226 seedlings were obtained, of which 90% were hybrid. In contrast, 105 G. hirsutum/G. thurberi crosses produced only 143 seedlings, but only one was hybrid. The hybrid seedlings were intermediate in phenotype to the parents and were sterile, as expected for triploids. The non-hybrid seedlings were identical to the upland cotton parents and were fertile. Given that one worker emasculated all of the flowers without prior knowledge of pollen source, chance accidental self-pollinations alone would not likely account for the difference between the G. armourianum and G. thurberi crosses. From six subsequent G. hirsutum/G. raimondii crosses in the greenhouse, 20 seedlings were produced, of which 19 were hybrid. In addition, in December 2007, AADD/DD crosses were made in Iguala, Mexico, using D-genome species that are difficult to grow and flower in Mississippi. Triploid hybrids from the earlier crosses were treated with chromosome doubling compounds and fertile plants have been recovered. The 13 D-genome diploid species are little-used but vast sources of genetic diversity for cotton improvement.