In this study, the acute toxicity of butyl benzyl phthalate (BBP) to freshwater cladoceran Moina macrocopa was tested, and its chronic effects on survival and reproduction of two successive generations of the cladoceran were studied using life-table demographic method. The results showed that the 48-hr LC50 of BBP for M. macrocopa was 3.69 mg l(-1). Compared to the blank controls, BBP at 125, 500, 1000 and 2000 microg l(-1) significantly shortened the life expectancy at birth, BBP at 125-2000 microg l(-1) decreased the net reproductive rate, and BBP at 500 and 1000 microg I(-1) shortened the generation time but increased the intrinsic rate of population increase of the parental M. macrocopa. BBP at 62.5,125, 500,1000 and 2000 microg l(-1) increased the intrinsic rate of population increase of the F1 generation. A significant dose-effect relationship existed between BBP concentration and life expectancy at birth, net reproductive rate as well as intrinsic rate of population increase of the parental M. macrocopa. The parental M. macrocopa were more sensitive in survival, development and reproduction to BBP than the F1 generation, but the reverse was also true in the population growth. Extending chronic toxicity tests to the second generation of M. macrocopa increased the cost-effectiveness of the assays.