Succinate tartrates (ST) are a mixture of organic builders (water softening agents) developed for use in commercial cleaning products. Extensive toxicological studies were conducted on the mixture and its two principal components (85% sodium tartrate monosuccinate (CAS No. 111451-13-9); 15% sodium tartrate disuccinate (CAS No. 111451-16-2)) to evaluate its environmental safety. Median effect concentrations of ST to 11 species of freshwater and marine fishes and invertebrates ranged from 110 to > 1000mg/l. No observed effect concentrations in chronic studies with 7 species of fishes, invertebrates and algae ranged from 16 to 560 mg/l. An inverse relationship between water hardness and toxicily was observed in tests with fish, invertebrates and algae. Low bioconceniration factors (<5) were estimated in uptake studies with fish. Sufficient data were compiled for ST to enable calculation of theoretical water quality criteria of 16 mg/l (criterion continuous concentration) and 44 mg/l (criterion maximum concentration). The low toxicity and bioconcentration potential demonstrated by these data are consistent with results of mammalian studies.