Abstract: The paper aims to examine the optimum combination of plant growth regulators (PGRs) and the type of explants on callus induction reactivity and the regenerative potentiality for suitable in vitro micropropagation of avocado‘Hass’. Using single factor and complete randomized block design via indirect organogenesis regeneration protocol, the present experiment was undertaken to explore the following: (1) the effect of 2,4-D/ NAA alone and different combinations of PGRs (BA+ 2,4-D/6-BA+ NAA) on callus induction via leaf explant from avocado‘Hass’; (2) the effect of different types of explants on callus induction from avocado‘Hass’; (3) the effect of 6-BA alone or combined with NAA for differentiation of callus. The results were: MS was used as the basic medium, (1) 2,4-D/NAA alone could induce callus with various degrees from leaf explant and there was a decrease in percentage of the extent of callus response and biomass with an increase in concentration of 2,4- D or NAA, the best frequency of callus response was obtained at 1.0 mg/L for 2,4- D/NAA, whose frequency was up to 45.3% and 20.2% respectively, but in terms of texture, callus induced by NAA was better; (2) the MS+1.0 mg/L NAA+1.0 mg/L 6-BA was the best medium for callus induction rate from leaf explant, and the highest rate reached 84%; (3) stem segment was the best kind of explant for callus formation and its frequency was up to 72.8% or higher, followed by petiole, however, the callus response was feeble when taking the leaf and stem apex as the explant. In conclusion, PGRs and the type of explants have a significantimpacton callus induction from avocado‘Hass’. The MS+1.0 mg/L NAA+1.0 mg/L 6-BA+30 g/L sucrose+7 g/L agar is the most appropriate medium for callus induction from avocado‘Hass’, and stem segment is the best kind of explant, but the callus shows no morphogenesis on any differentiation media.