Several factors suspected of contributing to N-nitrosodimethylamine (NDMA) formation were tested for significance with respect to formation in activated sludge. NDMA is of concern in situations where water is limited and treated wastewater is being used to recharge aquifers for drinking water. The significant factors in NDMA formation were determined to be nitrite and chlorine concentrations and the presence of dithiocarbamates, such as thiram, ziram and ferbam that contain a dimethylamine structure. The addition of nitrite did not promote NDMA formation without the presence of an organic precursor. NDMA yields varied with different batches of activated sludge; however, the same trends were observed. This variability indicated that the water quality itself and/or biological activity may contribute to the extent of NDMA formation from precursor compounds. Includes 18 references, tables, figures.