Lethality changes were investigated during development in 4 h metal exposed Caenorhabditis elegans. Exposure to examined metals caused severe lethality toxicities in L1- and L2-larvae, in L3-larvae exposed to examined metals at concentrations of 50 and 100 microM and to Pb, Hg, and Cr at the concentration of 2.5 microM, in L4-larvae exposed to examined metals at concentrations of 50 and 100 microM, and in adults exposed to Pb, Hg, and Cr at the concentration of 100 microM. Moreover, the lethality toxicities induced by Pb and Hg in L1 larvae for 4 h could be largely comparable to those in young adults for 24 h.