The characteristics relative to flowering, pollination, fertilization of some Thai Adenium obesum accessions were investigated at the Faculty of Agronomy, Hanoi University of Agriculture. The results showed that stamens and pistils mature at 48 hrs. and 72 hrs after anthesis, respectively. The pollen viability of different accessions was high, ranging from 90.1 + or - 3.9 percent to 95.7 + or - 0.7 percent. The fruit set of the cross combinations varied from 25 to 100 percent. The colour characteristics of hybrid fruits were regulated by the parental species. The fruit color was maternally controlled. The germination rate of Adenium obesum crossed seeds reached from 64 percent to 90.5 percent, and 25 percent to 97.4 percent of seedlings were obtained.