Local spotted salamander embryos (Ambystoma maculatum) were continuously exposed to diethylnitrosamine (DEN) in water concentrations of 0, 0.1, 0.5, and 1 ppt throughout embryogenesis. Malformations and growth retardation were observed during organogenesis and a dose-related response was established. At hatching, larvae were removed from carcinogen exposure and held in the laboratory for sixteen months. Throughout this period, daily observations were made on growth, health, and maintenance requirements of large numbers of captive salamanders. Subsequent histological analysis revealed no incidence of pathologic changes in several tissues sampled, including liver and kidney.