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The present investigation was carried out during two consecutive seasons 2015 and 2016 in fruit nursery of faculty of Agriculture at Moshtohor, Benha University, in order to throw some spotlight on the impact of some chemical substances (Ethylmethanesulphonate – EMS in 10, 20 and 30 ppm); (colchicine at concentrations of 1%, 2% and 3%) and (benzyl adenine – BA, at concentrations of 1,2% and 3%) on seed germination %, seed germination rate, some seedling growth measurements and cytological examination of root tip of Carica papaya cv. Solo. The treatments were arranged in complete randomized block design with nine replicates (polyethylene bags), however, each replicate was represented by two papaya seedlings. The seedlings were divided into three categories according to their growth vigor, each category represented by three replicates for each treatment and subsequently each category sampled by 60 seedlings for all studied treatments. Seedling growth and chromosomal behavior as imported by the three studied chemical substances were evaluated on the 1st week of December. Data obtained revealed that both BA at 2% and BA 3% increased significantly germination %, germination rate and growth measurements. On the contrary, the least significant increase was always in concomitant to EMS at 3% and colchicine at 3 % during both experimental seasons. Moreover, EMS was more inhibitor of cell division followed by BA than Colchicine. This may be due to more damage resulted by BA and EMS affected on DNA replication during mitosis.