The sensitivity of embryos of the penaeid shrimp, Trachypenaeus byrdi, to cooling, cryoprotectant exposure (dimethyl sulfoxide : DMSO, sucrose, methanol and glycerol), and hypersaline treatment was assessed in order to gain basic knowledge for cryopreservation procedures. In addition, cooling and DMSO exposure was evaluated in Penaeus stylirostris and T. byrdi nauplii. Morulae and advanced embryos (setae development stage) showed tolerance to cooling at 10°C, but were very sensitive to 0°C exposure. Methanol exposure at 12°C up to 2 M, was non-toxic for advanced embryos. DMSO toxicity was intermediate; no statistical decrease in survival (P>0.05) was measured at 0.5 M. Sucrose and glycerol were toxic to both embryo stages over 0.25 and 0.5 M, respectively. Morulae were more resistant to hypersaline treatment at 55 ppt than advanced embryos. Nauplii showed a better tolerance to cooling and DMSO exposure than embryos. These findings are being applied to develop a cryogenic protocol for penaeid embryos.