The estuarine environment is characterized by frequent fluctuations in salinity. Consequently, organisms used for environmental monitoring of estuaries must be euryhaline so that their laboratory responses to chemical pollutants are measured under the full range of salinity exposures experienced in the field. Neomysis integer and Praunus flexuosus are two potential candidates for use in environmental monitoring of European estuaries. The present study assesses the effects of salinity on survival, trace metal accumulation, and toxicity to these two mysid species. Neomysis integer was more euryhaline, showing 100% survival at 1 to 40@1000 compared with P. flexuosus, which showed 100% survival at salinities of 10 to 40@1000. Toxicity of the free cadmium ion to both species was unaffected by salinity, and 96-h LC50s ranged from 4.8 to 15 micrograms Cd2+/L for N. integer and from 12.3 to 16 micrograms Cd2+/L for P. flexuosus. The 7-d LC50s ranged from 1.0 to 4.2 and 4.8 to 5.3 micrograms Cd2+/L for N. integer and P. flexuosus, respectively. No effect of exposure salinity was found on cadmium body burdens of mysids exposed for 7 d to 0.5 and 1.0 microgram Cd2+/L. The results are discussed in terms of possible effects of osmoregulatory mechanisms on trace metal uptake, accumulation, and toxicity.