Chronic effects of triethylene glycol (TEG), a chemical frequently used as a carrier-solvent in toxicity tests, were investigated in a 23-day life-cycle toxicity test with a mysid (Mysidopsis bahia) and in a 28-day early life-stage toxicity test with the tidewater silverside (Menidia peninsulae). Test organisms were exposed to the same range of concentrations: seawater control, 3.2, 10, 32, 100, 320, and 1000 mg/L. Effects, if any, were measured by survival and reproduction for the mysids and survival and growth for the silversides. We concluded that no direct adverse effect should be expected as a result of using TEG at concentrations as high as 100 000 times (mysids) and 360 times (tidewater silversides) those recommended in ASTM drafts of standard practices (≤0.01 μL/L in Mysidopsis bahia life-cycle tests and ≤0.01 μL/L in tests with early life-stages of Menidia peninsulae) and that either a seawater or a TEG control may not be necessary.