Commonly cultivated mustard, Brassica juncea Coss, is an amphidiploid having in its genetic system the full 20-chromosome A genome (Brassica campestris) and the 16-chromosome B genome (Brassica nigra). Considerable natural variability exists under the A genome. These variations have been exploited for the artificial synthesis of B. juncea in order to breed improved mustard. The different combinations were studied both in their F1's and advanced amphidiploid generations in respect of their morphology, meiotic behaviour and fertility. Amphidiploids from leafy and rapiferous groups were generally bushy having arboreal habit. Some combinations from the leafy group result in types with luxuriant vegetative growth and can be used for fodder purposes. The amphiploids of ssp. rapifera did not give a swollen and enlarged root like the mother parent. None of the combinations from these two groups was promising in respect of oil and seed yield. Amphidiploids from the oleiferous group were both high seed and oil yielders and thus provide evidence that it formed one of the constituent parental species in the formation of oil yielding B. juncea.