There are at least seventeen indigenous wild cotton species in Australia, including 12 species (K genome) primarily distributed in the Kimberley area. The introgression of any useful features from the Kimberley cottons (2n=2x=26, KK) requires interspecific hybridization. We found that the Kimberley cottons had high pollen compatibility with cultivated tetraploids (2n=4x=52, AADD) when the tetraploids were used as female. The pollination between AD as female and K produced almost the same boll-set as intraspecific crossing, while the reciprocal crosses were unsuccessful. The hybrid bolls were smaller, had smaller seed and less seed per boll than the selfed bolls from the maternal parent plants. The hybrid seeds also germinated slowly and had lower germination percentage. The result demonstrated that the Kimberley cottons have pollen-stigma compatible factor(s) with AD, but that some postzygotic barriers exist. The variation in crossability varied with female parents and Kimberley species, with MDH-94 being more compatible than STV 453 with the Kimberley cottons. STV 453 x G. marchantii hybrid seed did not germinate and STV 453 x G. rotundifolium (NWA-22) hybrids died before emergence, indicating lethal factor(s) may exist in some Kimberley cotton accessions. Currently, we have obtained all interspecific hybrids between AD and seventeen Australian Gossypium and three crosses have been advanced to the BC2 generation.