Regulated and unregulated exhaust emissions from four late model 3-way catalyst passenger cars were measured over the urban dynamometer driving schedule of the Federal Test Procedure as a function of ambient temperature (50 F-81 F). Fuel economy, regulated emissions HC, CO, NOx, and unregulated emissions NH3, HCN, N2O, CH4, COS, H2S, SO2, SO4, and C6H6 were studied. It was found that reduced ambient temperature operation (less than 68 F) significantly increased the regulated emissions HC and CO, and slightly increased several unregulated emissions. Within the limitations of this study, none of the unregulated emissions were emitted at concentrations that could be considered hazardous to the public.