Abstract : Ammonium dinitramide (ADN) is a class 1.1 explosive oxidizer being considered for use in solid rocket propellant mixtures. Studies performed evaluating the toxicity of ADN have included an acute and subacute toxicity screen, a 90-day reproductive screen and three follow-on reproductive studies, electron paramagnetic resonance (EPR) spectroscopy studies, mutagenicity assays and a study evaluating the effects of ADN on hepatocytes in vitro. The LD50 in rats is 823 mg/kg, indicating ADN is moderately toxic. The results also indicated that ADN is a female reproductive toxicant in rats, causing implantation failure in early gestation; follow-on studies implied that ADN is embryotoxic. EPR studies indicated that ADN can decompose to form reactive nitrogen metabolites which can be harmful in biological systems. The hepatocyte studies suggested that ADN has the potential for directly affecting cellular DNA in vitro; these results are supported by traditional genotoxicity assays which reported that ADN is mutagenic.