Abstract: Hypocotyl,cotyledon,stem,leaf blade,leaf petiole explants of tomato were cultured on MSmedium supplemented with 2 mg/L BAand 0.2 mg/L IAAfor induction of calli and bud formation.Cytohistological observations on calli and bud formation were carried out. The results are as follows:there were significant differences in callus induction and growth among 5 kinds of explants mentioned above.Calli from hypocotyl and cotyledon explants were induced earlier than others,and had a faster growth rates than others.Buds differentia ted from calli were adventitious ones.Adventitious buds were generally formed on the peripheral parts of the calli,and also originated from the cambium-like cells surrounded by the vascular nodules.Adventitious roots originated from the pericycle.The caryological observation on callus paraffin section showed that as compared to the calli from hypocotyl,in the course of callus formation from cotyledon there were more kinds of nuclear division modes,but all these were of amitosis.