The products of xenobiotic reactions may pose risks greater than parent compounds. Products of concern include nitrosamines, which can be carcinogenic, mutagenic, and teratogenic. Nitrosamines may form in soil, lake water, sewage, and agricultural soils after applying nitrogen fertilizer and pesticides containing amine moieties. The herbicide atrazine has secondary amine moieties that react with nitrite to form N-nitrosoatrazine (NNAT). We studied NNAT formation, stability, and adsorption in water and soil. NNAT formed most readily in solution at pH 2-4 and in soil at pH ≤5. Acetic acid and fulvic acid promoted NNAT formation in water at pH 4-7. In soil NNAT formed after 7 d at pH 4 and 14 d at pH 5, but none was found at pH 6 and 7. No NNAT was detected in oversaturated or anaerobic soil, indicating the importance of oxygen in the reaction. Adsorption Kd and Koc values show greater adsorption of NNAT (average Kd = 5.93; Koc = 495) than atrazine (average K d = 2.71; Koc = 123) in Aksarben silty clay loam at agronomic pH. A larger desorption Kd indicates greater hysteresis of NNAT than atrazine. NNAT half-life in Aksarben soil was approximately 9 d, with degradation to atrazine and other compounds.