Embryos of the inland silverside, Menidia beryllina, were exposed to three known (or suspected) teratogens: (1) 2,4-dinitrophenol; (2,4-DNP), (2) 'produced water' (PW); and (3) naphthalene (NPH). Tests were conducted by placing single embryos in glass tissue culture tubes containing 6 ml of saline exposure media. Twenty tubes were used for each exposure concentration and controls. A severity-index based upon craniofacial, cardiovascular and skeletal terata was used to rank responses each day. The compounds tested caused teratogenic expressions in embryos and larvae exposed from the 2 to 4 cell and blastula stage through 7 to 8 days post-fertilization.