Somatic embryos of sweet potato have potential as synthetic seeds. The effects of abscisic acid (ABA) (0.0, 0.1, 1.0, 10.0 and 50.0 mM) were examined to improve synchrony and proliferation of somatic embryos. Transferring embryonic cultures at day 7 to solid medium with 0.1 or 1.0 mM ABA produced more torpedo and cotyledonary somatic embryos compared to those cultures transferred at day 0. The development of embryos in suspension culture supplemented with ABA was poor. However, when calli proliferation cultures were in gelled medium and pulsed with 0.1 mM ABA for 14 d, the number of somatic embryos increased. Proembryonic masses cultured in mannitol-containing medium Y 21X5 MPa increased embryo development and synchrony of embryo development. Thus, in this work ABA and mannitol have been shown to improve both the total number and the synchrony of sweet potato somatic embryos.