Specialized life history attributes of the cyprinodontiform fish, Rivulus marmoratus, allow continuous life cycle testing to reveal effects of chemicals or environmental stresses upon fertilization, fecundity, egg viability, embryonic development, sex ratios, frequency of growth or skeletal anomalies as well as other biological markers. The study reports responses in fecundity, viability of embryos and skeletal anomalies during and following cessation of exposure of parental fish to 1 and 2 mg/l nominal concentrations of the plasticizer, di-n-butylphthalate (DBP). Skeletal anomalies among offspring were classified as mild, moderate, or severe compared with non-deformed normal offspring. The frequency of skeletal anomalies increased from 4 percent (all categories combined) in controls, to 10 and 19 percent of the offspring from adults exposed to 1 and 2 mg/l DBP, respectively.