Trials on micropropagation of a new interspecific hybrid Hippeastrum x chmielii are being carried out in the Department of Ornamental Plants at the Warsaw Agricultural University. In 2002-2003, an effect of BA on bulblet differentiation from explants of different size was tested. Initial material consisted of bulblets (5-6 mm of diameter, mean fresh weight 0,164 g) produced in vitro on MS medium without growth regulators. The bulblets were cut into halves or quarters along the main axis and placed polarly or apolarly on MS medium without growth regulators or with BA 1, 2, 4 or 8 mg?dm-3. Regeneration proceeded at 24oC under white, fluorescent light (24 mumol?m-2?s-1) for 16 hours and 8 hours of darkness. On the explants with basal part in the medium, the cytokinin limited a number of bulblets regenerated on both types of explants. The bulbs cut into quarters formed more bulblets than those cut in halves. When the explants were placed apicaly, the numbers of regenerated bulblets were similar in all the treatments. Fresh weight of bulblets regenerated on smaller explants (1/4 of a bulb) was higher when explants were placed polarly. Polarity did not affect the weight of bulblets produced on larger explants.