N-Nitrosodimethylamine (NDMA) is an emerging contaminant of concern. N-nitrodimethylamine (DMNA) is a structural analog to NDMA. NDMA and DMNA have been found in drinking water, groundwater, and other media and are of concern due their toxicity. The authors evaluated biotransformation ofNDMAandDMNAby cultures enriched from contaminated groundwater growing on benzene, butane, methane, propane, or toluene. Maximum specific growth rates of enriched cultures on butane (μ max = 1.1 h -1) and propane (μ max = 0.65 h -1) were 1 to 2 orders of magnitude higher than those presented in the literature. Growth rates of mixed cultures grown on benzene (μ max = 1.3 h -1), methane (μ max = 0.09 h -1), and toluene (μ max = 0.99 h -1) in these studies were similar to those presented in the literature. NDMA biotransformation rates for methane oxidizers (υ max = 1.4 ng min -1 mg -1) and toluene oxidizers (υ max = 2.3 ng min -1 mg -1) were comparable to those presented in the literature, whereas the biotransformation rate for propane oxidizers (υ max =0.37 ng min -1 mg -1) was lower. NDMA biotransformation rates for benzene oxidizers (υ max = 1.02 ng min -1 mg -1) and butane oxidizers (υ max = 1.2 ng min -1 mg -1) were comparable to those reported for other primary substrates. These studies showed that DMNA biotransformation rates for benzene (υ max =0.79 ng min -1 mg -1), butane (υ max = 1.0 ng min -1 mg -1), methane (υ max = 2.1 ng min -1 mg -1), propane (υ max = 1.46 ng min -1 mg -1), and toluene (υ max = 0.52 ng min -1 mg -1) oxidizers were all comparable. These studies highlight potential bioremediation methods for NDMA and DMNA in contaminated groundwater. Copyright © 2012 Taylor and Francis Group, LLC.