Aquatic　organisms　are　usually　exposed　to　both　metal　pollution　and　eutrophication.　The　effects　of　phosphorus　levels　and　nitrogen　species　on　the　accumulation　and　biotoxicity　of　Cd　in　freshwater　zooplankton　Daphnia　magna　were　investigated.　Results　showed　that　P　in　water　could　increase　Cd　body　burden,　and　inhibit　metallothionein　(MT)　induction　in　D.　magna　after　Cd　exposure.　The　ratio　of　Cd　body　burden/MT　increased　markedly　with　increasing　P　levels,　accounting　for　phosphorus　in　water　could　intensify　Cd　biotoxicity　to　D.　magna.　Different　nitrogen　species　in　water　had　different　effects　on　Cd　accumulation　in　D.　magna,　with　the　order　NH4+-N　＞　NO3--N　＞　NH4+-N　and　NO3--N　in　waters,　which　could　disturb　MT　induction　in　D.　magna,　reinforcing　Cd　biotoxicity　to　D.　magna.　NO2--N　could　not　affect　Cd　biotoxicity　to　D.　magna,　whereas　NO2--N　itself　could　produce　toxic　effects　on　D.　magna　inducing　MT　synthesis.　The　ratio　of　metal　body　burden/MT　was　more　suitable　to　predict　metal　toxicity　to　D.　magna　than　metal　body　burden　or　MT　alone.